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Lewmar · tunnel thruster · bow or stern
Lewmar 185TT GEN 2: specs, price and the boats it fits
It gives 128 to 214 lb of push, across four sizes. Lewmar's own chart puts it on boats of 51 to 60 ft. It runs on 12 V or 24 V.
- Haul-out to install
- DIY 2 of 5: wiring prep only
- 3-year warranty
Choose a size
The Lewmar 185TT GEN 2 Tunnel Thruster comes in four sizes. Each has its own price, wiring and boats it suits. Pick one and the page below shows that size.
Every size side by side
| Size | Push | Voltage | Lewmar’s boat length | Price |
|---|---|---|---|---|
| 185TT 3.0kW | 128 lb (58 kgf) | 12 V | Not published | $1,912 |
| 185TT 4.0kW | 143 lb (65 kgf) | 12 V | Not published | $2,339 |
| 185TT 5.0kW | 181 lb (82 kgf) | 12 V | Not published | $2,708 |
| 185TT 6.0kW | 214 lb (97 kgf) | 12 or 24 V | Not published | $3,427 to $4,825 |
From the database. The figures are Lewmar’s and the dealers’.
Quick stats
- Thrust 128 lb 58 kgf, Lewmar's rating
- Boat length 36 to 45 ft Lewmar's chart, by windage. See below
- Price per lb of thrust $14.94 Unit only. $71 to $148 installed
- Voltage 12 V As sold
- Battery at 12 V 330 CCA One battery, near the thruster
- Run limit 3 min In one direction, then fault mode
- To install it Haul-out The boat comes out of the water
- Anodes $20.89 A change, at Fisheries Supply
Quick stats
- Thrust 143 lb 65 kgf, Lewmar's rating
- Boat length 41 to 50 ft Lewmar's chart, by windage. See below
- Price per lb of thrust $16.36 Unit only. $68 to $138 installed
- Voltage 12 V As sold
- Battery at 12 V 470 CCA One battery, near the thruster
- Run limit 3 min In one direction, then fault mode
- To install it Haul-out The boat comes out of the water
- Anodes $20.89 A change, at Fisheries Supply
Quick stats
- Thrust 181 lb 82 kgf, Lewmar's rating
- Boat length 46 to 55 ft Lewmar's chart, by windage. See below
- Price per lb of thrust $14.96 Unit only. $56 to $111 installed
- Voltage 12 V As sold
- Battery at 12 V 480 CCA One battery, near the thruster
- Run limit 3 min In one direction, then fault mode
- To install it Haul-out The boat comes out of the water
- Anodes $20.89 A change, at Fisheries Supply
Quick stats
- Thrust 214 lb 97 kgf, Lewmar's rating
- Boat length 51 to 60 ft Lewmar's chart, by windage. See below
- Price per lb of thrust $16.01 Unit only. $52 to $105 installed
- Voltage 12 V or 24 V As sold
- Battery at 12 V 700 CCA One battery, near the thruster
- Run limit 3 min In one direction, then fault mode
- To install it Haul-out The boat comes out of the water
- Anodes $20.89 A change, at Fisheries Supply
About the Lewmar 185TT GEN 2
The 185TT Gen 2 is Lewmar’s main bow thruster for mid-size cruisers and trawlers: one five-blade propeller in a 185 mm tube, equal push both ways, and a sealed gearbox with no oil reservoir to fit or top up. Four motors share the tube, from 3 kW to 6 kW, giving 128 to 214 lb of push on 12 V. Pick a size and the page shows its own figures.
Defender sells the four from $1,912 to $3,427, the lowest of the three stores we checked. The 5 kW ($2,708) gives far more push than the 4 kW ($2,339) for almost the same current. A 24 V build of the 6 kW is a special order at Fisheries Supply for $4,825. The box holds the thruster, its control box and a motor cable; the tube, controls, fuse and battery switch are about $533 to $1,358 more, and a battery with cable and charger $583 to $1,135. See every part.
Read more
At 12 V the 6 kW wants more copper than a dealer cuts, so keep its battery close. One owner of a heavy Ocean Alexander motor yacht found the biggest 12 V size small for her, yet it never hit its time limit. Another lost a 6 kW’s gear hub at 22 months. Motors and controls carry one year of warranty.
The full spec sheet for a yard sits lower down, and the Lewmar thruster review covers Lewmar’s whole range.
Where this summary comes from (9 sources, read 13 October 2026)
- Defender listing (the database’s price)
- Lippert store, 185TT 3.0 kW (price read 2 Oct 2026)
- Fisheries Supply, 185TT 3.0 kW (price read 2 Oct 2026)
- Fisheries Supply, Lewmar thrusters (24 V 185TT 6.0 kW, item 590013LEW, special order)
- Trawler Forum, 2017: owners of big boats on Lewmar 185TT units
- Trawler Forum, 2021: a 185TT 6.0 hub assembly gone at 22 months
- Lewmar Gen 2 TT installation manual 559231 Iss.3 (three minutes one way, then fault mode; warranty one year on motors and controls)
- Lewmar, About (making boat hardware in Havant, England, since 1946)
- Lippert Components acquires Lewmar Marine Limited, 1 August 2019
Will the Lewmar 185TT GEN 2 Tunnel Thruster steer your boat?
45 FT TRAWLER · BOW · 15 KT WIND
Every knot figure here is wind speed, not boat speed or current.
On a 45 ft trawler the Lewmar 185TT GEN 2 Tunnel Thruster (128 lb) steers her in a 15 knot breeze. Her bow needs about 135 lb from a tunnel to steer her in a 15 knot breeze. Its 128 lb lands within 15 percent of that figure, which this site counts as enough.
The finder leaves it off her list. It shows the 185TT 4.0kW for her instead.
The Lewmar 185TT GEN 2 Tunnel Thruster on a trawler, by length
- 25 ft26 kt
- 30 ft22 kt
- 35 ft19 kt
- 40 ft17 kt
- 45 ft15 kt
- 50 ft13 kt
- 55 ft12 kt
- 60 ft11 kt
- 65 ft10 kt
- 70 ft9 kt
- 75 ft9 kt
- 80 ft8 kt
Outlined: the finder does not list it at that length (under 13 kt, far more than she needs, or outside Lewmar’s own length range).
- Under 10 kt
- 10 to 15 kt
- 15 to 20 kt: the sweet spot
- Over 20 kt: more than she needs
Prices are the low end of the installed total, from our estimate. For your own boat, drive and installer, the finder prices each unit.
Is it right for your boat?
Every kind of boat it fits, by length
| Boat | Full thrust at 15 knots | Still a fit, in lighter wind | Lewmar’s chart |
|---|---|---|---|
| Pontoon & tritoon | Not listed. A pontoon has no hull body between the logs to bore a tunnel through, and nobody sells one for these boats. | ||
| Sailboat | 32 to 45 ft | 46 to 51 ftfull thrust to about 13 knots at 51 ft | 41 to 45 ftas the 185TT 3.0, class B |
| Houseboat | 30 to 33 ft | 34 to 38 ftfull thrust to about 13 knots at 38 ft | 36 to 40 ftas the 185TT 3.0, class C |
| Catamaran | 37 to 52 ft | 53 to 59 ftfull thrust to about 13 knots at 59 ft | 36 to 40 ftas the 185TT 3.0, class C |
| Trawler | 32 to 45 ft | 46 to 51 ftfull thrust to about 13 knots at 51 ft | 36 to 40 ftas the 185TT 3.0, class C |
| Motor yacht | 35 to 45 ft | 46 to 51 ftfull thrust to about 13 knots at 51 ft | 36 to 40 ftas the 185TT 3.0, class C |
| Bass & flats | Not listed. Nobody sells a tunnel kit for these hulls, and a bass boat’s shallow planing bow has almost no depth to hold one. | ||
| Wake & ski boats | Not listed. Nobody sells a tunnel kit for these hulls. | ||
| Express cruiser | 41 to 57 ft | 58 to 65 ftfull thrust to about 13 knots at 65 ft | 41 to 45 ftas the 185TT 3.0, class B |
| Center console | No length. More thrust than the boat needs. | ||
The Lewmar 185TT GEN 2 Tunnel Thruster against each kind of boat, in a 15 knot wind. Our sizing, from the finder’s own rules, beside Lewmar's chart.
The first column is where one unit gives all the thrust the boat needs in 15 knots. The second is where the finder still lists it: the unit steers her in a 13 or 14 knot wind, within 15 percent of the 15 knot breeze this site sizes for. On a boat shorter than the first column’s shortest length, the unit is more than the boat needs.
How we size it
Our figure is the longest boat one unit can steer in a 15 knot wind. It is a range because each kind of boat catches the wind differently. Here a houseboat gets full thrust to 33 ft, and an express cruiser to 57 ft.
The table tries the Lewmar 185TT GEN 2 Tunnel Thruster on each kind of boat, at every length that kind of boat is built in. The wind is 15 knots and the rules are the finder’s own. A length counts as a fit when the unit gives the thrust that boat needs at the bow. The listing prints no boat length, so thrust alone decides. Lewmar's own figures are in the opening lines.
Reading Lewmar’s chart. Lewmar publishes a selection guide, checked 15 September 2026, on a dealer’s copy. It names a model by boat length, from 30 to 90 ft, for a The area of the boat the wind can push on: the hull sides, the cabin, the mast and rigging, or the canopy. A tall, boxy boat has a lot of it, and wind force does not care how slowly you are moving. class and a wind band. Our 15 knots falls in its lightest band, 11 to 16 knots.
The Lewmar 185TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 128 lb (58 kgf) as the 185TT 3.0. That tunnel unit is on the chart, so the column shows what the chart says for it. Which class a kind of boat falls in is our reading of its windage. The chart starts at 30 ft.
It is sized for six kinds of boat here. For your own boat, the finder gives an answer that also counts your drive and who does the installing. The compare page sets this unit beside others.
What it costs installed
A yard job, everything in. Our estimate.
| Boat | Total installed |
|---|---|
| 30 ft | $8,688 to $11,197$68 to $87 a lb of thrust |
| 50 ft | $9,138 to $18,997$71 to $148 a lb of thrust |
| 65 ft | $9,388 to $19,727$73 to $154 a lb of thrust |
From the shortest to the longest boat it is sized for.
What is in each total
These totals are our estimate of a yard job: the unit’s price, plus a yard’s hours at $160 to $180 an hour, plus the batteries, cable and charger, plus the other parts the box does not hold. A Lifting the boat out of the water on a travel lift or a trailer so work can be done below the waterline. It is billed separately from the job itself. adds $540 to $3,140 at these lengths, with 5 to 7 days out of the water, worked from eight yards’ own rate cards. The hours come from what owners and yards report. The cost page builds the same figures line by line.
| Boat length | The unit | Yard labor | Haul-out | Batteries, cable, charger | Other parts |
|---|---|---|---|---|---|
| 30 ft | $1,912 | $5,120 to $5,760about 32 hours | $540 to $1,450 | $583 to $717 | $533 to $1,358 |
| 50 ft | $1,912 | $5,120 to $12,60032 to 70 hours | $990 to $2,410 | $583 to $717 | $533 to $1,358 |
| 65 ft | $1,912 | $5,120 to $12,60032 to 70 hours | $1,240 to $3,140 | $583 to $717 | $533 to $1,358 |
For every length in the table above.
How the batteries, cable and charger add up. We price a battery bank close to the thruster, as the makers recommend, with 10 to 20 ft of cable out and back: red for the positive, black for the negative, cut to length. The low end is the cheapest battery that meets the figure and the shorter run; the high end is a sealed (AGM) battery and the longer run. The charger is a NOCO GEN5X2 two-bank shore charger.
Batteries and lugs are priced at Fisheries Supply and the cable and charger at Defender, read 26 October 2026.
- At 12 V: one 12 V battery, at least 330 CCA (Lewmar’s minimum), $257 for the battery; Lewmar’s cable table gives 4/0 AWG: $180 to $314 for the red and black cable and the lugs; a GEN5X2 charger, $146.
The sizing and the costs on this page are estimates, for guidance only and without warranty. They are no quote, and nobody has inspected your boat. Check them against the maker’s manual and your yard before you rely on them. Terms of use.
DIY breakdown
DIY levels
- Level 5: Owner install. No yard, no electrician.
- Level 4: You install it, electrician connects. You mount and wire it; a marine electrician makes the final connections.
- Level 3: Split with the yard. The yard does the below-waterline part; you do the wiring.
- Level 2: Wiring prep only. The yard installs the unit and does the hull work; you do the wiring prep.
- Level 1: Yard job. A qualified professional does all of it.
You Yard Electrician. The bar is labor hours; a haul-out is a note.
How we rate DIYYou: 4 to 16 hours Yard: 32 to 70 hours Electrician: 2 to 4 hours Plus a haul-out.
Your part needs:Heavy battery cableCrimping big lugs
Every step, and who does it
- Cut, bond and fair the tunnel; fit the gear leg, motor and propeller Yard 32 to 70 hours The low end is two crew over two days, the job as owners describe it on the forums. The high end rises with boat length between two real billed figures: 32 hours at 35 ft, and the largest invoice we hold, 70 hours at 47 ft.
- Mount the battery box, switch and fuse holder; run and secure the cables You 4 to 16 hours Our estimate. No maker times this step, and a first-time owner is slower than a yard, so the range is wide.
- Final connections at the battery and the motor, load test Electrician 2 to 4 hours Our estimate. Nobody publishes a time for the final connections and test on their own.
A qualified marine electrician should make the final connections and test them before first use. Hours are labor only.
Will the Lewmar 185TT GEN 2 Tunnel Thruster steer your boat?
47 FT TRAWLER · BOW · 15 KT WIND
Every knot figure here is wind speed, not boat speed or current.
On a 47 ft trawler the Lewmar 185TT GEN 2 Tunnel Thruster (143 lb) steers her in a 15 knot breeze. Her bow needs about 148 lb from a tunnel to steer her in a 15 knot breeze. Its 143 lb lands within 15 percent of that figure, which this site counts as enough.
The finder leaves it off her list. It shows the 185TT 5.0kW for her instead.
The Lewmar 185TT GEN 2 Tunnel Thruster on a trawler, by length
- 25 ft28 kt
- 30 ft23 kt
- 35 ft20 kt
- 40 ft18 kt
- 45 ft15 kt
- 50 ft14 kt
- 55 ft12.6 kt
- 60 ft12 kt
- 65 ft11 kt
- 70 ft10 kt
- 75 ft9 kt
- 80 ft9 kt
Outlined: the finder does not list it at that length (under 13 kt, far more than she needs, or outside Lewmar’s own length range).
- Under 10 kt
- 10 to 15 kt
- 15 to 20 kt: the sweet spot
- Over 20 kt: more than she needs
Prices are the low end of the installed total, from our estimate. For your own boat, drive and installer, the finder prices each unit.
Is it right for your boat?
Every kind of boat it fits, by length
| Boat | Full thrust at 15 knots | Still a fit, in lighter wind | Lewmar’s chart |
|---|---|---|---|
| Pontoon & tritoon | Not listed. A pontoon has no hull body between the logs to bore a tunnel through, and nobody sells one for these boats. | ||
| Sailboat | 34 to 48 ft | 49 to 55 ftfull thrust to about 13 knots at 55 ft | 46 to 50 ftas the 185TT 4.0, class B |
| Houseboat | 30 to 36 ft | 37 to 40 ftfull thrust to about 13 knots at 40 ft | 41 to 45 ftas the 185TT 4.0, class C |
| Catamaran | 39 to 55 ft | 56 to 62 ftfull thrust to about 13 knots at 62 ft | 41 to 45 ftas the 185TT 4.0, class C |
| Trawler | 34 to 47 ft | 48 to 54 ftfull thrust to about 13 knots at 54 ft | 41 to 45 ftas the 185TT 4.0, class C |
| Motor yacht | 35 to 47 ft | 48 to 54 ftfull thrust to about 13 knots at 54 ft | 41 to 45 ftas the 185TT 4.0, class C |
| Bass & flats | Not listed. Nobody sells a tunnel kit for these hulls, and a bass boat’s shallow planing bow has almost no depth to hold one. | ||
| Wake & ski boats | Not listed. Nobody sells a tunnel kit for these hulls. | ||
| Express cruiser | 43 to 61 ft | 62 to 65 ftfull thrust to about 14 knots at 65 ft | 46 to 50 ftas the 185TT 4.0, class B |
| Center console | No length. More thrust than the boat needs. | ||
The Lewmar 185TT GEN 2 Tunnel Thruster against each kind of boat, in a 15 knot wind. Our sizing, from the finder’s own rules, beside Lewmar's chart.
The first column is where one unit gives all the thrust the boat needs in 15 knots. The second is where the finder still lists it: the unit steers her in a 13 or 14 knot wind, within 15 percent of the 15 knot breeze this site sizes for. On a boat shorter than the first column’s shortest length, the unit is more than the boat needs.
How we size it
Our figure is the longest boat one unit can steer in a 15 knot wind. It is a range because each kind of boat catches the wind differently. Here a houseboat gets full thrust to 36 ft, and an express cruiser to 61 ft.
The table tries the Lewmar 185TT GEN 2 Tunnel Thruster on each kind of boat, at every length that kind of boat is built in. The wind is 15 knots and the rules are the finder’s own. A length counts as a fit when the unit gives the thrust that boat needs at the bow. The listing prints no boat length, so thrust alone decides. Lewmar's own figures are in the opening lines.
Reading Lewmar’s chart. Lewmar publishes a selection guide, checked 15 September 2026, on a dealer’s copy. It names a model by boat length, from 30 to 90 ft, for a The area of the boat the wind can push on: the hull sides, the cabin, the mast and rigging, or the canopy. A tall, boxy boat has a lot of it, and wind force does not care how slowly you are moving. class and a wind band. Our 15 knots falls in its lightest band, 11 to 16 knots.
The Lewmar 185TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 143 lb (65 kgf) as the 185TT 4.0. That tunnel unit is on the chart, so the column shows what the chart says for it. Which class a kind of boat falls in is our reading of its windage. The chart starts at 30 ft.
It is sized for six kinds of boat here. For your own boat, the finder gives an answer that also counts your drive and who does the installing. The compare page sets this unit beside others.
What it costs installed
A yard job, everything in. Our estimate.
| Boat | Total installed |
|---|---|
| 30 ft | $9,295 to $11,939$65 to $83 a lb of thrust |
| 50 ft | $9,745 to $19,739$68 to $138 a lb of thrust |
| 65 ft | $9,995 to $20,469$70 to $143 a lb of thrust |
From the shortest to the longest boat it is sized for.
What is in each total
These totals are our estimate of a yard job: the unit’s price, plus a yard’s hours at $160 to $180 an hour, plus the batteries, cable and charger, plus the other parts the box does not hold. A Lifting the boat out of the water on a travel lift or a trailer so work can be done below the waterline. It is billed separately from the job itself. adds $540 to $3,140 at these lengths, with 5 to 7 days out of the water, worked from eight yards’ own rate cards. The hours come from what owners and yards report. The cost page builds the same figures line by line.
| Boat length | The unit | Yard labor | Haul-out | Batteries, cable, charger | Other parts |
|---|---|---|---|---|---|
| 30 ft | $2,339 | $5,120 to $5,760about 32 hours | $540 to $1,450 | $763 to $1,032 | $533 to $1,358 |
| 50 ft | $2,339 | $5,120 to $12,60032 to 70 hours | $990 to $2,410 | $763 to $1,032 | $533 to $1,358 |
| 65 ft | $2,339 | $5,120 to $12,60032 to 70 hours | $1,240 to $3,140 | $763 to $1,032 | $533 to $1,358 |
For every length in the table above.
How the batteries, cable and charger add up. We price a battery bank close to the thruster, as the makers recommend, with 10 to 20 ft of cable out and back: red for the positive, black for the negative, cut to length. The low end is the cheapest battery that meets the figure and the shorter run; the high end is a sealed (AGM) battery and the longer run. The charger is a NOCO GEN5X2 two-bank shore charger.
Batteries and lugs are priced at Fisheries Supply and the cable and charger at Defender, read 26 October 2026.
- At 12 V: one 12 V battery, at least 470 CCA (Lewmar’s minimum), $257 for the battery; Lewmar’s cable table gives 2 x 3/0 AWG, priced on 2 x 4/0 AWG, the nearest size cut to length: $360 to $629 for the red and black cable and the lugs; a GEN5X2 charger, $146.
The sizing and the costs on this page are estimates, for guidance only and without warranty. They are no quote, and nobody has inspected your boat. Check them against the maker’s manual and your yard before you rely on them. Terms of use.
DIY breakdown
DIY levels
- Level 5: Owner install. No yard, no electrician.
- Level 4: You install it, electrician connects. You mount and wire it; a marine electrician makes the final connections.
- Level 3: Split with the yard. The yard does the below-waterline part; you do the wiring.
- Level 2: Wiring prep only. The yard installs the unit and does the hull work; you do the wiring prep.
- Level 1: Yard job. A qualified professional does all of it.
You Yard Electrician. The bar is labor hours; a haul-out is a note.
How we rate DIYYou: 4 to 16 hours Yard: 32 to 70 hours Electrician: 2 to 4 hours Plus a haul-out.
Your part needs:Heavy battery cableCrimping big lugs
Every step, and who does it
- Cut, bond and fair the tunnel; fit the gear leg, motor and propeller Yard 32 to 70 hours The low end is two crew over two days, the job as owners describe it on the forums. The high end rises with boat length between two real billed figures: 32 hours at 35 ft, and the largest invoice we hold, 70 hours at 47 ft.
- Mount the battery box, switch and fuse holder; run and secure the cables You 4 to 16 hours Our estimate. No maker times this step, and a first-time owner is slower than a yard, so the range is wide.
- Final connections at the battery and the motor, load test Electrician 2 to 4 hours Our estimate. Nobody publishes a time for the final connections and test on their own.
A qualified marine electrician should make the final connections and test them before first use. Hours are labor only.
Will the Lewmar 185TT GEN 2 Tunnel Thruster steer your boat?
53 FT TRAWLER · BOW · 15 KT WIND
Every knot figure here is wind speed, not boat speed or current.
On a 53 ft trawler the Lewmar 185TT GEN 2 Tunnel Thruster (181 lb) steers her in a 15 knot breeze. Her bow needs about 188 lb from a tunnel to steer her in a 15 knot breeze. Its 181 lb lands within 15 percent of that figure, which this site counts as enough.
The finder leaves it off her list. It shows the 185TT 6.0kW for her instead.
The Lewmar 185TT GEN 2 Tunnel Thruster on a trawler, by length
- 25 ft31 kt
- 30 ft26 kt
- 35 ft22 kt
- 40 ft20 kt
- 45 ft17 kt
- 50 ft16 kt
- 55 ft14 kt
- 60 ft13 kt
- 65 ft12 kt
- 70 ft11 kt
- 75 ft10 kt
- 80 ft10 kt
Outlined: the finder does not list it at that length (under 13 kt, far more than she needs, or outside Lewmar’s own length range).
- Under 10 kt
- 10 to 15 kt
- 15 to 20 kt: the sweet spot
- Over 20 kt: more than she needs
Prices are the low end of the installed total, from our estimate. For your own boat, drive and installer, the finder prices each unit.
Is it right for your boat?
Every kind of boat it fits, by length
| Boat | Full thrust at 15 knots | Still a fit, in lighter wind | Lewmar’s chart |
|---|---|---|---|
| Pontoon & tritoon | Not listed. A pontoon has no hull body between the logs to bore a tunnel through, and nobody sells one for these boats. | ||
| Sailboat | 38 to 54 ft | 55 to 62 ftfull thrust to about 13 knots at 62 ft | 51 to 55 ftas the 185TT 5.0, class B |
| Houseboat | 30 to 40 ft | 41 to 46 ftfull thrust to about 13 knots at 46 ft | 46 to 50 ftas the 185TT 5.0, class C |
| Catamaran | 43 to 61 ft | 62 to 70 ftfull thrust to about 13 knots at 70 ft | 46 to 50 ftas the 185TT 5.0, class C |
| Trawler | 38 to 53 ft | 54 to 61 ftfull thrust to about 13 knots at 61 ft | 46 to 50 ftas the 185TT 5.0, class C |
| Motor yacht | 38 to 53 ft | 54 to 61 ftfull thrust to about 13 knots at 61 ft | 46 to 50 ftas the 185TT 5.0, class C |
| Bass & flats | Not listed. Nobody sells a tunnel kit for these hulls, and a bass boat’s shallow planing bow has almost no depth to hold one. | ||
| Wake & ski boats | Not listed. Nobody sells a tunnel kit for these hulls. | ||
| Express cruiser | 48 to 65 ft | None | 51 to 55 ftas the 185TT 5.0, class B |
| Center console | No length. More thrust than the boat needs. | ||
The Lewmar 185TT GEN 2 Tunnel Thruster against each kind of boat, in a 15 knot wind. Our sizing, from the finder’s own rules, beside Lewmar's chart.
The first column is where one unit gives all the thrust the boat needs in 15 knots. The second is where the finder still lists it: the unit steers her in a 13 or 14 knot wind, within 15 percent of the 15 knot breeze this site sizes for. On a boat shorter than the first column’s shortest length, the unit is more than the boat needs.
How we size it
Our figure is the longest boat one unit can steer in a 15 knot wind. It is a range because each kind of boat catches the wind differently. Here a houseboat gets full thrust to 40 ft, and an express cruiser to 65 ft.
The table tries the Lewmar 185TT GEN 2 Tunnel Thruster on each kind of boat, at every length that kind of boat is built in. The wind is 15 knots and the rules are the finder’s own. A length counts as a fit when the unit gives the thrust that boat needs at the bow. The listing prints no boat length, so thrust alone decides. Lewmar's own figures are in the opening lines.
Reading Lewmar’s chart. Lewmar publishes a selection guide, checked 15 September 2026, on a dealer’s copy. It names a model by boat length, from 30 to 90 ft, for a The area of the boat the wind can push on: the hull sides, the cabin, the mast and rigging, or the canopy. A tall, boxy boat has a lot of it, and wind force does not care how slowly you are moving. class and a wind band. Our 15 knots falls in its lightest band, 11 to 16 knots.
The Lewmar 185TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 181 lb (82 kgf) as the 185TT 5.0. That tunnel unit is on the chart, so the column shows what the chart says for it. Which class a kind of boat falls in is our reading of its windage. The chart starts at 30 ft.
It is sized for six kinds of boat here. For your own boat, the finder gives an answer that also counts your drive and who does the installing. The compare page sets this unit beside others.
What it costs installed
A yard job, everything in. Our estimate.
| Boat | Total installed |
|---|---|
| 30 ft | $9,664 to $12,308$53 to $68 a lb of thrust |
| 50 ft | $10,114 to $20,108$56 to $111 a lb of thrust |
| 70 ft | $10,454 to $21,078$58 to $116 a lb of thrust |
From the shortest to the longest boat it is sized for.
What is in each total
These totals are our estimate of a yard job: the unit’s price, plus a yard’s hours at $160 to $180 an hour, plus the batteries, cable and charger, plus the other parts the box does not hold. A Lifting the boat out of the water on a travel lift or a trailer so work can be done below the waterline. It is billed separately from the job itself. adds $540 to $3,380 at these lengths, with 5 to 7 days out of the water, worked from eight yards’ own rate cards. The hours come from what owners and yards report. The cost page builds the same figures line by line.
| Boat length | The unit | Yard labor | Haul-out | Batteries, cable, charger | Other parts |
|---|---|---|---|---|---|
| 30 ft | $2,708 | $5,120 to $5,760about 32 hours | $540 to $1,450 | $763 to $1,032 | $533 to $1,358 |
| 50 ft | $2,708 | $5,120 to $12,60032 to 70 hours | $990 to $2,410 | $763 to $1,032 | $533 to $1,358 |
| 70 ft | $2,708 | $5,120 to $12,60032 to 70 hours | $1,330 to $3,380 | $763 to $1,032 | $533 to $1,358 |
For every length in the table above.
How the batteries, cable and charger add up. We price a battery bank close to the thruster, as the makers recommend, with 10 to 20 ft of cable out and back: red for the positive, black for the negative, cut to length. The low end is the cheapest battery that meets the figure and the shorter run; the high end is a sealed (AGM) battery and the longer run. The charger is a NOCO GEN5X2 two-bank shore charger.
Batteries and lugs are priced at Fisheries Supply and the cable and charger at Defender, read 26 October 2026.
- At 12 V: one 12 V battery, at least 480 CCA (Lewmar’s minimum), $257 for the battery; Lewmar’s cable table gives 2 x 4/0 AWG: $360 to $629 for the red and black cable and the lugs; a GEN5X2 charger, $146.
The sizing and the costs on this page are estimates, for guidance only and without warranty. They are no quote, and nobody has inspected your boat. Check them against the maker’s manual and your yard before you rely on them. Terms of use.
DIY breakdown
DIY levels
- Level 5: Owner install. No yard, no electrician.
- Level 4: You install it, electrician connects. You mount and wire it; a marine electrician makes the final connections.
- Level 3: Split with the yard. The yard does the below-waterline part; you do the wiring.
- Level 2: Wiring prep only. The yard installs the unit and does the hull work; you do the wiring prep.
- Level 1: Yard job. A qualified professional does all of it.
You Yard Electrician. The bar is labor hours; a haul-out is a note.
How we rate DIYYou: 4 to 16 hours Yard: 32 to 70 hours Electrician: 2 to 4 hours Plus a haul-out.
Your part needs:Heavy battery cableCrimping big lugs
Every step, and who does it
- Cut, bond and fair the tunnel; fit the gear leg, motor and propeller Yard 32 to 70 hours The low end is two crew over two days, the job as owners describe it on the forums. The high end rises with boat length between two real billed figures: 32 hours at 35 ft, and the largest invoice we hold, 70 hours at 47 ft.
- Mount the battery box, switch and fuse holder; run and secure the cables You 4 to 16 hours Our estimate. No maker times this step, and a first-time owner is slower than a yard, so the range is wide.
- Final connections at the battery and the motor, load test Electrician 2 to 4 hours Our estimate. Nobody publishes a time for the final connections and test on their own.
A qualified marine electrician should make the final connections and test them before first use. Hours are labor only.
Will the Lewmar 185TT GEN 2 Tunnel Thruster steer your boat?
58 FT TRAWLER · BOW · 15 KT WIND
Every knot figure here is wind speed, not boat speed or current.
On a 58 ft trawler the Lewmar 185TT GEN 2 Tunnel Thruster (214 lb) steers her in a 15 knot breeze. Her bow needs about 225 lb from a tunnel to steer her in a 15 knot breeze. Its 214 lb lands within 15 percent of that figure, which this site counts as enough.
The finder lists it for her.
The Lewmar 185TT GEN 2 Tunnel Thruster on a trawler, by length
- 25 ft34 kt
- 30 ft28 kt
- 35 ft24 kt
- 40 ft21 kt
- 45 ft19 kt
- 50 ft17 kt
- 55 ft15 kt
- 60 ft14 kt
- 65 ft13 kt
- 70 ft12 kt
- 75 ft11 kt
- 80 ft11 kt
Outlined: the finder does not list it at that length (under 13 kt, far more than she needs, or outside Lewmar’s own length range).
- Under 10 kt
- 10 to 15 kt
- 15 to 20 kt: the sweet spot
- Over 20 kt: more than she needs
Prices are the low end of the installed total, from our estimate. For your own boat, drive and installer, the finder prices each unit.
Is it right for your boat?
Every kind of boat it fits, by length
| Boat | Full thrust at 15 knots | Still a fit, in lighter wind | Lewmar’s chart |
|---|---|---|---|
| Pontoon & tritoon | Not listed. A pontoon has no hull body between the logs to bore a tunnel through, and nobody sells one for these boats. | ||
| Sailboat | 41 to 59 ft | 60 to 67 ftfull thrust to about 13 knots at 67 ft | 56 to 60 ftas the 185TT 6.0, class B |
| Houseboat | 31 to 43 ft | 44 to 50 ftfull thrust to about 13 knots at 50 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Catamaran | 46 to 67 ft | 68 to 76 ftfull thrust to about 13 knots at 76 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Trawler | 41 to 58 ft | 59 to 66 ftfull thrust to about 13 knots at 66 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Motor yacht | 41 to 58 ft | 59 to 66 ftfull thrust to about 13 knots at 66 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Bass & flats | Not listed. Nobody sells a tunnel kit for these hulls, and a bass boat’s shallow planing bow has almost no depth to hold one. | ||
| Wake & ski boats | Not listed. Nobody sells a tunnel kit for these hulls. | ||
| Express cruiser | 52 to 65 ft | None | 56 to 60 ftas the 185TT 6.0, class B |
| Center console | No length. More thrust than the boat needs. | ||
The Lewmar 185TT GEN 2 Tunnel Thruster against each kind of boat, in a 15 knot wind. Our sizing, from the finder’s own rules, beside Lewmar's chart.
The first column is where one unit gives all the thrust the boat needs in 15 knots. The second is where the finder still lists it: the unit steers her in a 13 or 14 knot wind, within 15 percent of the 15 knot breeze this site sizes for. On a boat shorter than the first column’s shortest length, the unit is more than the boat needs.
How we size it
Our figure is the longest boat one unit can steer in a 15 knot wind. It is a range because each kind of boat catches the wind differently. Here a houseboat gets full thrust to 43 ft, and a catamaran to 67 ft.
The table tries the Lewmar 185TT GEN 2 Tunnel Thruster on each kind of boat, at every length that kind of boat is built in. The wind is 15 knots and the rules are the finder’s own. A length counts as a fit when the unit gives the thrust that boat needs at the bow. The listing prints no boat length, so thrust alone decides. Lewmar's own figures are in the opening lines.
Reading Lewmar’s chart. Lewmar publishes a selection guide, checked 15 September 2026, on a dealer’s copy. It names a model by boat length, from 30 to 90 ft, for a The area of the boat the wind can push on: the hull sides, the cabin, the mast and rigging, or the canopy. A tall, boxy boat has a lot of it, and wind force does not care how slowly you are moving. class and a wind band. Our 15 knots falls in its lightest band, 11 to 16 knots.
The Lewmar 185TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 214 lb (97 kgf) as the 185TT 6.0. That tunnel unit is on the chart, so the column shows what the chart says for it. Which class a kind of boat falls in is our reading of its windage. The chart starts at 30 ft.
It is sized for six kinds of boat here. For your own boat, the finder gives an answer that also counts your drive and who does the installing. The compare page sets this unit beside others.
What it costs installed
A yard job, everything in. Our estimate.
| Boat | Total installed |
|---|---|
| 31 ft | $10,496 to $14,578$49 to $68 a lb of thrust |
| 55 ft | $11,026 to $22,568$52 to $105 a lb of thrust |
| 76 ft | $11,376 to $23,588$53 to $110 a lb of thrust |
From the shortest to the longest boat it is sized for.
What is in each total
These totals are our estimate of a yard job: the unit’s price, plus a yard’s hours at $160 to $180 an hour, plus the batteries, cable and charger, plus the other parts the box does not hold. A Lifting the boat out of the water on a travel lift or a trailer so work can be done below the waterline. It is billed separately from the job itself. adds $550 to $3,670 at these lengths, with 5 to 7 days out of the water, worked from eight yards’ own rate cards. The hours come from what owners and yards report. The cost page builds the same figures line by line.
| Boat length | The unit | Yard labor | Haul-out | Batteries, cable, charger | Other parts |
|---|---|---|---|---|---|
| 31 ft | $3,427 to $4,825 | $5,120 to $5,760about 32 hours | $550 to $1,500 | $866 to $1,135 | $533 to $1,358 |
| 55 ft | $3,427 to $4,825 | $5,120 to $12,60032 to 70 hours | $1,080 to $2,650 | $866 to $1,135 | $533 to $1,358 |
| 76 ft | $3,427 to $4,825 | $5,120 to $12,60032 to 70 hours | $1,430 to $3,670 | $866 to $1,135 | $533 to $1,358 |
For every length in the table above.
How the batteries, cable and charger add up. We price a battery bank close to the thruster, as the makers recommend, with 10 to 20 ft of cable out and back: red for the positive, black for the negative, cut to length. The low end is the cheapest battery that meets the figure and the shorter run; the high end is a sealed (AGM) battery and the longer run. The charger is a NOCO GEN5X2 two-bank shore charger.
Batteries and lugs are priced at Fisheries Supply and the cable and charger at Defender, read 26 October 2026.
- At 12 V: one 12 V battery, at least 700 CCA (Lewmar’s minimum), $360 for the battery; Lewmar’s cable table gives Over 2 x 4/0 AWG, and that is more copper than the heaviest cable the dealer sells, so this part is a floor, priced on 2 x 4/0 AWG, the nearest size cut to length: $360 to $629 for the red and black cable and the lugs; a GEN5X2 charger, $146.
- At 24 V: two 12 V batteries in series, at least 370 CCA each (Lewmar’s minimum), $513 for both; Lewmar’s cable table gives 2 x 2/0 AWG: $228 to $403 for the red and black cable and the lugs; a GEN5X2 charger, $146.
The sizing and the costs on this page are estimates, for guidance only and without warranty. They are no quote, and nobody has inspected your boat. Check them against the maker’s manual and your yard before you rely on them. Terms of use.
DIY breakdown
DIY levels
- Level 5: Owner install. No yard, no electrician.
- Level 4: You install it, electrician connects. You mount and wire it; a marine electrician makes the final connections.
- Level 3: Split with the yard. The yard does the below-waterline part; you do the wiring.
- Level 2: Wiring prep only. The yard installs the unit and does the hull work; you do the wiring prep.
- Level 1: Yard job. A qualified professional does all of it.
You Yard Electrician. The bar is labor hours; a haul-out is a note.
How we rate DIYYou: 4 to 16 hours Yard: 32 to 70 hours Electrician: 2 to 4 hours Plus a haul-out.
Your part needs:Heavy battery cableCrimping big lugs
Every step, and who does it
- Cut, bond and fair the tunnel; fit the gear leg, motor and propeller Yard 32 to 70 hours The low end is two crew over two days, the job as owners describe it on the forums. The high end rises with boat length between two real billed figures: 32 hours at 35 ft, and the largest invoice we hold, 70 hours at 47 ft.
- Mount the battery box, switch and fuse holder; run and secure the cables You 4 to 16 hours Our estimate. No maker times this step, and a first-time owner is slower than a yard, so the range is wide.
- Final connections at the battery and the motor, load test Electrician 2 to 4 hours Our estimate. Nobody publishes a time for the final connections and test on their own.
A qualified marine electrician should make the final connections and test them before first use. Hours are labor only.
Related videos
One from Lewmar’s own channel and two from other channels. Each one is labeled. They play from YouTube only when you tap. Take any claim in a video back to the figures on this page, which are the ones we checked.
Know before you buy
What sets this model apart, what it costs to keep, and what to weigh.
Price per pound of thrust
$14.94 a lb The unit’s price over its published thrust, on the smallest size. The bars are Lewmar’s next sizes and the nearest other makers.Controls
The solenoid, the ICU control box and a 2 m motor loom are in the box. The panel, its loom, the fuse and holder are bought.
- Lewmar Gen 2 single joystick control (589268), $373.53 at Fisheries Supply.
- Lewmar Gen 2 AUX control loom, 7 m (589802), $69.10 at Fisheries Supply.
Anodes
$20.89 a change- Anode kit (589350): $20.89 at Fisheries Supply.
They sit below the waterline, so a change means a haul-out or a diver.
Service and warranty
Lewmar gives 3 years, but 1 on electric motors and their electrical equipment and on electronic controls. Service by anyone but an authorized Lewmar representative can void it. Removal, transport and installation costs are not covered.
See Lewmar’s warranty Lewmar's Gen 2 installation manual.Special mentions
Battery: at 12 V it wants one battery of 330 CCA or more, Lewmar's figure. The cheapest that meets it is the Lifeline GPL-1400T AGM starting, $256.72. Check your own bank.
Charger: a NOCO GEN5X2 two-bank shore charger, $146.41. It is the one our estimate prices.
Lewmar sells it for either end, so it can go at the bow or the stern.
Dealer prices at Fisheries Supply, read 26 October 2026.What to weigh
The boat comes out of the water to install it: it needs a tunnel bore below the waterline.
Lewmar prints no single length band for it. Its selection chart gives one by windage: 51 to 60 ft at 15 knots, across the kinds of boat in the table. The boat table is our sizing alone.
Short pushes only: Lewmar rates the motor for 3 min at a stretch.
At 12 V it draws 700 A, so the battery cable is heavy and the battery sits close to it.
Parts for the Lewmar 185TT GEN 2 Tunnel Thruster
See the Lewmar 185TT GEN 2 manualSearch for the number as printed here, with no spaces. Prices are each dealer’s on the day shown, before shipping and tax. Check the plate on your motor before you order: some parts change with the tunnel size, the voltage or the year.
For the install what the box leaves you to buy
The manual button above opens it a dealer's copy (the maker publishes none we could find). It has the hull, wiring and fuse figures for this model.
From Lewmar’s Gen 2 TT installation manual 559231 and the RT manual 55110070, Iss.3 and Iss.4, read 30 September 2026.
- In the box
- The motor, the solenoid and its loom, the ICU control box, a 2 m motor loom, the saddle, gasket, hub, propeller, anode kit and fixings. The RT ships with its own housing and actuator.
- Bought separately
- Under Accessories: the control panels, the panel looms, the fuse holders and ANL fuses, the automatic battery switch. "The installation MUST have a battery switch". The tunnel fits a Lewmar saddle.
- Charging
- The manual sizes the battery by cranking amps and says to "ensure batteries are fully charged before switching on the main power". It gives no rule on a charger, a feed or a bank of its own.
The manual’s words, page 12: “Battery crank capacity should be at least equal to the thruster current.”
The “other parts” line in the estimate above covers these parts as a range, $533 to $1,358 at Fisheries Supply’s prices on 30 September 2026 and 26 October 2026, because the exact items depend on your boat. The batteries, cable and charger have a line of their own. The cost page has what every maker says about each part.
Tunnel tube
Fisheries Supply lists it as “Lewmar fiberglass tunnel tube, 185 mm bore, 1000 mm”.
Sold in lengths from about 39 to 59 in. This is the shortest: the yard cuts the tube to the width of your hull at the thruster.
Control panel
Fisheries Supply lists it as “Lewmar Gen 2 single joystick control”.
Control cable, panel to thruster
Fisheries Supply lists it as “Lewmar Gen 2 AUX control loom, 7 m”.
Sold in lengths from 7 to 18 m. This is the shortest: measure the run from the helm to the thruster and buy the length that reaches.
Main fuse
Ask for 250 A (Lewmar 589008). This one is for the 3.0kW at 12 V version.
Lewmar's figure for the 590006, TT 185 3.0kw 12v (Gen 2 installation manual, Iss.3). Not listed at Fisheries Supply; ask a Lewmar dealer.
Main fuse
Ask for 400 A (Lewmar 589010). This one is for the 4.0kW at 12 V version.
Lewmar's figure for the 590008, TT 185 4.0Kw 12v (Gen 2 installation manual, Iss.3). Not listed at Fisheries Supply; ask a Lewmar dealer.
Main fuse
Ask for 400 A (Lewmar 589010). This one is for the 5.0kW at 12 V version.
Lewmar's figure for the 590010, TT 185 5.0Kw 12v (Gen 2 installation manual, Iss.3). Not listed at Fisheries Supply; ask a Lewmar dealer.
Main fuse
Ask for 500 A (Lewmar 589011). This one is for the 6.0kW at 12 V version.
Lewmar's figure for the 590012, TT 185 6.0Kw 12v (Gen 2 installation manual, Iss.3). Not listed at Fisheries Supply; ask a Lewmar dealer.
Main fuse
Ask for 325 A (Lewmar 589009). This one is for the 6.0kW 24 V version.
Lewmar's figure for the 590013, TT 185 6.0Kw 24v (Gen 2 installation manual, Iss.3). Not listed at Fisheries Supply; ask a Lewmar dealer.
Fuse holder
Ask for Lewmar fuse holder 589006 (T1) or 589013 (T2). This one is for the 3.0kW at 12 V and 6.0kW 24 V version.
Ask the dealer who sells the fuse.
Fuse holder
Ask for Lewmar fuse holder 589013 (T2). This one is for the 4.0kW at 12 V and 5.0kW at 12 V and 6.0kW at 12 V version.
Ask the dealer who sells the fuse.
Battery switch
Fisheries Supply lists it as “m-Series 300 A battery switch, on/off”. This one is for the 3.0kW at 12 V version.
Rated at or above the 250 A main fuse. If your manual names its own switch, use that one.
Battery switch
Fisheries Supply lists it as “HD-Series 600 A battery switch, on/off”. This one is for the 4.0kW at 12 V and 5.0kW at 12 V version.
Rated at or above the 400 A main fuse. If your manual names its own switch, use that one.
Battery switch
Fisheries Supply lists it as “HD-Series 600 A battery switch, on/off”. This one is for the 6.0kW at 12 V version.
Rated at or above the 500 A main fuse. If your manual names its own switch, use that one.
Battery switch
Fisheries Supply lists it as “e-Series 350 A battery switch, on/off”. This one is for the 6.0kW 24 V version.
Rated at or above the 325 A main fuse. If your manual names its own switch, use that one.
Control-circuit fuse holder
Fisheries Supply lists it as “Waterproof in-line ATO/ATC fuse holder”.
Lewmar's control unit (ICU) draws 8 A and has a slow-blow fuse inside; fuse its own supply to suit the wire, and use cable rated for 8 A.
Batteries
Fisheries Supply lists it as “Lifeline GPL-1400T AGM starting”. This one is for the 3.0kW at 12 V version.
One at 330 CCA or more. The cheapest listing that meets it.
Batteries
Fisheries Supply lists it as “Lifeline GPL-1400T AGM starting”. This one is for the 4.0kW at 12 V version.
One at 470 CCA or more. The cheapest listing that meets it.
Batteries
Fisheries Supply lists it as “Lifeline GPL-1400T AGM starting”. This one is for the 5.0kW at 12 V version.
One at 480 CCA or more. The cheapest listing that meets it.
Batteries
Fisheries Supply lists it as “Optima BlueTop SC27DM Group 27 AGM”. This one is for the 6.0kW at 12 V version.
One at 700 CCA or more. The cheapest listing that meets it.
Batteries
Fisheries Supply lists it as “Lifeline GPL-1400T AGM starting”. This one is for the 6.0kW 24 V version.
You need 2, each at 370 CCA or more, in series for 24 V. The cheapest listing that meets it.
Battery cable, red and black
Defender lists it as “Ancor tinned battery cable 4/0 AWG, cut to length, red or black”. This one is for the 3.0kW at 12 V version.
You need 10 ft of each color. For about 20 ft of cable in all, out and back. Measure your run and check it against the cable table in the manual: never go smaller than it asks for.
Battery cable, red and black
Defender lists it as “Ancor tinned battery cable 4/0 AWG, cut to length, red or black”. This one is for the 4.0kW at 12 V and 5.0kW at 12 V and 6.0kW at 12 V version.
You need 10 ft of each color, twice over (20 ft of each). For about 20 ft of cable in all, out and back. Measure your run and check it against the cable table in the manual: never go smaller than it asks for.
Battery cable, red and black
Defender lists it as “Ancor tinned battery cable 2/0 AWG, cut to length, red or black”. This one is for the 6.0kW 24 V version.
You need 10 ft of each color, twice over (20 ft of each). For about 20 ft of cable in all, out and back. Measure your run and check it against the cable table in the manual: never go smaller than it asks for.
Cable lugs
Fisheries Supply lists it as “Tin-plated starter lugs, 4/0 AWG, bag of 10”. This one is for the 3.0kW at 12 V version.
The listing runs $47.52 to $49.44 by stud size. Eight ends on one run, with two spare.
Cable lugs
Fisheries Supply lists it as “Tin-plated starter lugs, 4/0 AWG, bag of 10”. This one is for the 4.0kW at 12 V and 5.0kW at 12 V and 6.0kW at 12 V version.
You need 2 bags. The listing runs $47.52 to $49.44 by stud size. Eight ends on one run, with two spare.
Cable lugs
Fisheries Supply lists it as “Tin-plated starter lugs, 2/0 AWG, bag of 10”. This one is for the 6.0kW 24 V version.
You need 2 bags. The listing runs $27.96 to $29.36 by stud size. Eight ends on one run, with two spare.
Charger
Fisheries Supply lists it as “GEN5X2 on-board charger, 10 A, 2 banks”.
Or a DC-to-DC charger from the house system: ask the electrician.
Outside the hull replacement parts in the water
Anode kit
The metal that wears away in the water so the drive does not. Lewmar calls it “ANODE KIT”.
Propeller
The propeller on the drive. Lewmar calls it “PROPELLER AND WASHER”.
One propeller on the 185TT tunnel thruster.
Drive pin (breaks to protect the drive)
The pin that locks the propeller to its shaft. Lewmar calls it “DRIVE PIN”.
Defender sells a two-pack of this pin as 559017A.
Tunnel gasket
It keeps water out of the joint it sits in. Lewmar calls it “TUNNEL GASKET”.
Inside the boat replacement parts on board
Solenoid (the motor switch)
The heavy switch that sends battery power to the motor. Lewmar calls it “SOLENOID 4/5.0 12V”. This one is for the 12 V version. It fits the 4.0kW and 5.0kW sizes on this page.
For the 12 V 4.0 and 5.0 kW only. The 24 V units take B11129.
Solenoid (the motor switch)
The heavy switch that sends battery power to the motor. Lewmar calls it “SOLENOID 6.0 12V”. This one is for the 12 V version. It fits the 6.0kW size on this page.
For the 12 V 6.0 kW only. The 24 V 6.0 kW takes B11129.
Solenoid (the motor switch)
The heavy switch that sends battery power to the motor. Lewmar calls it “SOLENOID 2.2 / SOLENOID 3.0 12V”. This one is for the 140TT 2.2 kW; 185TT 3.0 kW 12 V version. It fits the 3.0kW size on this page.
The 140TT 2.0 kW takes B12526. On the 185TT this one is for the 3.0 kW 12 V only.
Solenoid (the motor switch)
The heavy switch that sends battery power to the motor. Lewmar calls it “SOLENOID 4/5/6.0 24V; SOLENOID 8.0”. This one is for the 24 V version. It fits the 6.0kW 24V size on this page.
For the 24 V units only. The 12 V 185TT units take a different solenoid.
Controller box (the ICU)
The electronics that run the motor when you press the panel. Lewmar calls it “GEN2 TT ICU”.
The 250TT parts list prints its ICU as 589834, the same number as its solenoid loom, so we list no ICU number for the 250TT.
Main fuse, 250 A
The main fuse at the battery, in the rating the maker gives. Lewmar calls it “250 A ANL TYPE FUSE”. It fits the 3.0kW size on this page.
The rating the manual gives for each model it fits. Lewmar sells it as an ANL fuse.
Main fuse, 325 A
The main fuse at the battery, in the rating the maker gives. Lewmar calls it “325 A ANL TYPE FUSE”. It fits the 6.0kW 24V size on this page.
The rating the manual gives for each model it fits. Lewmar sells it as an ANL fuse.
Main fuse, 400 A
The main fuse at the battery, in the rating the maker gives. Lewmar calls it “400 A ANL TYPE FUSE”. It fits the 4.0kW and 5.0kW sizes on this page.
The manual gives 400 A for the 300TT 15.0 kW 48 V (590035) and for the aluminum 300TT 10.8 kW, but 500 A for the bronze 10.8 kW (590034).
Main fuse, 500 A
The main fuse at the battery, in the rating the maker gives. Lewmar calls it “500 A ANL TYPE FUSE”. It fits the 6.0kW size on this page.
The manual gives 500 A for the 300TT 10.8 kW with the bronze gearbox (590034) but 400 A for the aluminum one (590033). West Marine lists this fuse against the 300TT 15.0 kW (590035); the manual gives that model 400 A.
Control panel, dual joystick (bow and stern)
The control at the helm. Lewmar calls it “Controller, Dual Joystick”.
Control panel, dual pad (bow and stern)
The control at the helm. Lewmar calls it “Controller, Dual Pad”.
Control panel, single joystick
The control at the helm. Lewmar calls it “Controller, Single Joystick”.
Control panel, single pad
The control at the helm. Lewmar calls it “Controller, Single Pad”.
Replacement motor
The electric motor that turns the propeller. Lewmar calls it “MOTOR ASSY 3.0KW 12V MX”. This one is for the 3.0 kW 12 V version. It fits the 3.0kW size on this page.
The standard motor. The manual lists a separate IP (ignition protected) motor.
Replacement motor
The electric motor that turns the propeller. Lewmar calls it “MOTOR ASSY 4.0KW 12V MX”. This one is for the 4.0 kW 12 V version. It fits the 4.0kW size on this page.
The standard motor. The manual lists a separate IP (ignition protected) motor.
Replacement motor
The electric motor that turns the propeller. Lewmar calls it “MOTOR ASSY 5.0KW 12V MX”. This one is for the 5.0 kW 12 V version. It fits the 5.0kW size on this page.
The standard motor. The manual lists a separate IP (ignition protected) motor.
Replacement motor
The electric motor that turns the propeller. Lewmar calls it “MOTOR ASSY 6.0KW 12V MX”. This one is for the 6.0 kW 12 V version. It fits the 6.0kW size on this page.
The standard motor. The manual lists a separate IP (ignition protected) motor.
Replacement motor
The electric motor that turns the propeller. Lewmar calls it “MOTOR ASSY 6.0KW 24V MX”. This one is for the 6.0 kW 24 V version. It fits the 6.0kW 24V size on this page.
The standard motor. The manual lists a separate IP (ignition protected) motor.
No part matches. Try the number without spaces, or the part’s name.
The install parts are matched to Lewmar’s own figures and priced at Fisheries Supply, with the battery cable at Defender, cut to length.
Spare part numbers come from Lewmar’s parts pages and manuals. A dealer may sell a part we have not priced. Search for the number.
Other sizes and close alternatives
- Size down Lewmar 185TT GEN 2 Package 128 lb · $2,239
- Size up Lewmar 250TT GEN 2 308 lb · $4,949
- Other maker Sleipner SE80/185T 212 lb · $3,285
- Other maker Max Power CT100-IP 212 lb · $4,237
- Other maker Quick BTQ 185 six sizes, 121 to 209 lb · $3,476 to $7,511
The other makers listed are the nearest match each makes, of the same style and for the same end, within a quarter of its thrust. The compare page lists every model, and the thruster index lists every model with a page here.
For the yard and the installer
Every published figure, with its source.
Full spec sheet
| Thrust and motor | |
|---|---|
| Thrust | 128 lb (58 kgf) As printed: Thrust: 128 lbs |
| Motor | 3 kW |
| Voltage | 12 V |
| Run limit | 3 min in one direction, then fault mode |
| Installation | |
| Type | Tunnel, fixed mount |
| End of the boat | Bow or stern |
| Tunnel diameter | 185 mm |
| What it does to the hull | Tunnel bore below the waterline |
| Haul-out to install it | Yes |
| Maker’s boat length | 36 to 45 ftLewmar's selection chart, by windage; the listing prints none |
| Price and ordering | |
| Price | $1,912 equipment only, a dealer's price, defender.com, 26 October 2026 |
| Part number | 5900136.0kW 24 V, 24 V DC |
| Documents | |
| Manual | Installation manual (PDF)a dealer's copy (the maker publishes none we could find) |
| The site’s review | Lewmar thruster review |
Every published figure the site holds for the Lewmar 185TT GEN 2 Tunnel Thruster, with where each came from.
Draw, cable, fuse and battery at each voltage
These are the maker’s own figures, at each voltage it is sold at. The cable is the size for the shortest run in the maker’s table. A longer run may need heavier cable, and the wiring calculator works that out for your own boat.
| Voltage | Draw | Maker’s cable | Fuse | Battery | Run limit |
|---|---|---|---|---|---|
| 12 V | 330 Anominal draw | 4/0 AWG, the one size Lewmar gives for this model, for any run up to 49 ft of cable counted out and backGen 2 installation manual, Iss.3 | 250 AGen 2 installation manual, Iss.3 | Crank capacity at least the 330 A draw, Lewmar's ruleLewmar Gen 2 installation manual | 3 min in one direction, then fault modeGen 2 installation manual |
The Lewmar 185TT GEN 2 Tunnel Thruster’s draw, cable, fuse, battery and run limit, as the maker publishes them.
- At 12 V: size the cable for your run, or check the battery you have.
The tunnel: length and depth rules
Tunnel length. A minimum suggested tunnel length of twice the diameter. Lewmar’s installation manual.
Depth below the waterline. One tunnel diameter below the waterline to keep air out of the tunnel, with 0.75 of a diameter the minimum. Gen 2 TT installation manual, 559231 Iss.3 (2018).
Our notes from the manual and listings
In the box: The solenoid, the ICU control box and a 2 m motor loom are in the box. The panel, its loom, the fuse and holder are bought.
3.0kW
Single propeller in a 185 mm tunnel with a stainless gearbox. This row covers four motors: 3.0, 4.0, 5.0 and 6.0 kW at 12 V. It is one Defender listing with a size menu and no part number shown until the option is chosen. The Gen 2 manual rates the 3.0 kW at 58 kgf (128 lb) and 20 kg.
It draws 330 A at 12 V behind a 250 A fuse. The cable is at least 95 mm² to 15 m of total run, battery to thruster and back. It rates the 6.0 kW at 97 kgf (214 lb), 27 kg, a 500 A fuse and 700 A on 300 mm² to 22 m.
Every fuse in the manual's table sits below the stated draw, and the 4.0 and 5.0 kW units draw ten amps apart for 17 kgf of difference. Lewmar's whole battery rule is that crank capacity should at least equal the thruster current. Run it in one direction for more than three minutes and the system enters fault mode.
A thermal switch stops a hot motor, and the manual says wait 20 minutes. The panel powers itself down after 15 minutes idle. The tunnel goes one diameter below the waterline (three quarters at minimum) and at least two diameters long. The anode is checked after three or four months on a new install, then yearly.
The manual says brush the carbon dust out of the motor, especially on an aluminum boat. Three years' warranty on paper, but one year on electric motors, associated electrical equipment and electronic controls. Service by anyone but an authorized Lewmar representative voids the warranty, and removal and reinstalling are not covered. Lewmar publishes no boat length.
Fisheries Supply's listings say 35 to 45 ft for the 3.0 kW, 40 to 55 for the 5.0, and two different bands for the 6.0 kW by voltage. The same part number is dearer at Fisheries Supply and dearer still at Lippert's own store. Defender's is the lowest of the three.
4.0kW
The 4.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 65 kgf (143 lb), 20 kg and a 400 A fuse. It gives 470 A at 12 V on at least 150 mm² cable to 16 m of total run. The 5.0 kW unit above it draws only ten amps more. Those are most of what fails on an electric thruster.
Lewmar publishes no boat length for any unit. Lippert's own store lists the same part number well above Defender.
5.0kW
The 5.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 82 kgf (181 lb), 27 kg, a 400 A fuse below its own 480 A at 12 V, on at least 185 mm² cable to 21 m of total run. Fisheries Supply's listing says 40 to 55 ft.
6.0kW
The 6.0 kW 185TT Gen 2, the biggest single-propeller Lewmar. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, a 500 A fuse below its own 700 A at 12 V, on at least 300 mm² cable to 22 m of total run, the biggest cable in the table. Fisheries Supply says 46 to 66 ft for this 12 V unit and 45 to 55 for the 24 V one, two bands for one motor.
6.0kW 24 V
The 6.0 kW 185TT Gen 2 at 24 V. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, with a 325 A fuse.
Where each point above comes from
- Lewmar sells it for either end, so it can go at the bow or the stern.The maker's listing
- The boat comes out of the water to install it: it needs a tunnel bore below the waterline.The mounting: a bore through the hull, or a housing recessed into it
- Lewmar prints no single length band for it. Its selection chart gives one by windage: 36 to 45 ft at 15 knots, across the kinds of boat in the table. The boat table is our sizing alone.Lewmar's Thruster Selection Guide, checked 15 September 2026
For the yard and the installer
Every published figure, with its source.
Full spec sheet
| Thrust and motor | |
|---|---|
| Thrust | 143 lb (65 kgf) As printed: Thrust: 143 lbs |
| Motor | 4 kW |
| Voltage | 12 V |
| Run limit | 3 min in one direction, then fault mode |
| Installation | |
| Type | Tunnel, fixed mount |
| End of the boat | Bow or stern |
| Tunnel diameter | 185 mm |
| What it does to the hull | Tunnel bore below the waterline |
| Haul-out to install it | Yes |
| Maker’s boat length | 41 to 50 ftLewmar's selection chart, by windage; the listing prints none |
| Price and ordering | |
| Price | $2,339 equipment only, a dealer's price, defender.com, 26 October 2026 |
| Part number | 5900136.0kW 24 V, 24 V DC |
| Documents | |
| Manual | Installation manual (PDF)a dealer's copy (the maker publishes none we could find) |
| The site’s review | Lewmar thruster review |
Every published figure the site holds for the Lewmar 185TT GEN 2 Tunnel Thruster, with where each came from.
Draw, cable, fuse and battery at each voltage
These are the maker’s own figures, at each voltage it is sold at. The cable is the size for the shortest run in the maker’s table. A longer run may need heavier cable, and the wiring calculator works that out for your own boat.
| Voltage | Draw | Maker’s cable | Fuse | Battery | Run limit |
|---|---|---|---|---|---|
| 12 V | 470 Anominal draw | 2 x 3/0 AWG per leg, the one size Lewmar gives for this model, for any run up to 52 ft of cable counted out and backGen 2 installation manual, Iss.3 | 400 AGen 2 installation manual, Iss.3 | Crank capacity at least the 470 A draw, Lewmar's ruleLewmar Gen 2 installation manual | 3 min in one direction, then fault modeGen 2 installation manual |
The Lewmar 185TT GEN 2 Tunnel Thruster’s draw, cable, fuse, battery and run limit, as the maker publishes them.
- At 12 V: size the cable for your run, or check the battery you have.
The tunnel: length and depth rules
Tunnel length. A minimum suggested tunnel length of twice the diameter. Lewmar’s installation manual.
Depth below the waterline. One tunnel diameter below the waterline to keep air out of the tunnel, with 0.75 of a diameter the minimum. Gen 2 TT installation manual, 559231 Iss.3 (2018).
Our notes from the manual and listings
In the box: The solenoid, the ICU control box and a 2 m motor loom are in the box. The panel, its loom, the fuse and holder are bought.
3.0kW
Single propeller in a 185 mm tunnel with a stainless gearbox. This row covers four motors: 3.0, 4.0, 5.0 and 6.0 kW at 12 V. It is one Defender listing with a size menu and no part number shown until the option is chosen. The Gen 2 manual rates the 3.0 kW at 58 kgf (128 lb) and 20 kg.
It draws 330 A at 12 V behind a 250 A fuse. The cable is at least 95 mm² to 15 m of total run, battery to thruster and back. It rates the 6.0 kW at 97 kgf (214 lb), 27 kg, a 500 A fuse and 700 A on 300 mm² to 22 m.
Every fuse in the manual's table sits below the stated draw, and the 4.0 and 5.0 kW units draw ten amps apart for 17 kgf of difference. Lewmar's whole battery rule is that crank capacity should at least equal the thruster current. Run it in one direction for more than three minutes and the system enters fault mode.
A thermal switch stops a hot motor, and the manual says wait 20 minutes. The panel powers itself down after 15 minutes idle. The tunnel goes one diameter below the waterline (three quarters at minimum) and at least two diameters long. The anode is checked after three or four months on a new install, then yearly.
The manual says brush the carbon dust out of the motor, especially on an aluminum boat. Three years' warranty on paper, but one year on electric motors, associated electrical equipment and electronic controls. Service by anyone but an authorized Lewmar representative voids the warranty, and removal and reinstalling are not covered. Lewmar publishes no boat length.
Fisheries Supply's listings say 35 to 45 ft for the 3.0 kW, 40 to 55 for the 5.0, and two different bands for the 6.0 kW by voltage. The same part number is dearer at Fisheries Supply and dearer still at Lippert's own store. Defender's is the lowest of the three.
4.0kW
The 4.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 65 kgf (143 lb), 20 kg and a 400 A fuse. It gives 470 A at 12 V on at least 150 mm² cable to 16 m of total run. The 5.0 kW unit above it draws only ten amps more. Those are most of what fails on an electric thruster.
Lewmar publishes no boat length for any unit. Lippert's own store lists the same part number well above Defender.
5.0kW
The 5.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 82 kgf (181 lb), 27 kg, a 400 A fuse below its own 480 A at 12 V, on at least 185 mm² cable to 21 m of total run. Fisheries Supply's listing says 40 to 55 ft.
6.0kW
The 6.0 kW 185TT Gen 2, the biggest single-propeller Lewmar. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, a 500 A fuse below its own 700 A at 12 V, on at least 300 mm² cable to 22 m of total run, the biggest cable in the table. Fisheries Supply says 46 to 66 ft for this 12 V unit and 45 to 55 for the 24 V one, two bands for one motor.
6.0kW 24 V
The 6.0 kW 185TT Gen 2 at 24 V. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, with a 325 A fuse.
Where each point above comes from
- Lewmar sells it for either end, so it can go at the bow or the stern.The maker's listing
- The boat comes out of the water to install it: it needs a tunnel bore below the waterline.The mounting: a bore through the hull, or a housing recessed into it
- Lewmar prints no single length band for it. Its selection chart gives one by windage: 41 to 50 ft at 15 knots, across the kinds of boat in the table. The boat table is our sizing alone.Lewmar's Thruster Selection Guide, checked 15 September 2026
For the yard and the installer
Every published figure, with its source.
Full spec sheet
| Thrust and motor | |
|---|---|
| Thrust | 181 lb (82 kgf) As printed: Thrust: 181 lbs |
| Motor | 5 kW |
| Voltage | 12 V |
| Run limit | 3 min in one direction, then fault mode |
| Installation | |
| Type | Tunnel, fixed mount |
| End of the boat | Bow or stern |
| Tunnel diameter | 185 mm |
| What it does to the hull | Tunnel bore below the waterline |
| Haul-out to install it | Yes |
| Maker’s boat length | 46 to 55 ftLewmar's selection chart, by windage; the listing prints none |
| Price and ordering | |
| Price | $2,708 equipment only, a dealer's price, defender.com, 26 October 2026 |
| Part number | 5900136.0kW 24 V, 24 V DC |
| Documents | |
| Manual | Installation manual (PDF)a dealer's copy (the maker publishes none we could find) |
| The site’s review | Lewmar thruster review |
Every published figure the site holds for the Lewmar 185TT GEN 2 Tunnel Thruster, with where each came from.
Draw, cable, fuse and battery at each voltage
These are the maker’s own figures, at each voltage it is sold at. The cable is the size for the shortest run in the maker’s table. A longer run may need heavier cable, and the wiring calculator works that out for your own boat.
| Voltage | Draw | Maker’s cable | Fuse | Battery | Run limit |
|---|---|---|---|---|---|
| 12 V | 480 Anominal draw | 2 x 4/0 AWG per leg, the one size Lewmar gives for this model, for any run up to 68 ft of cable counted out and backGen 2 installation manual, Iss.3 | 400 AGen 2 installation manual, Iss.3 | Crank capacity at least the 480 A draw, Lewmar's ruleLewmar Gen 2 installation manual | 3 min in one direction, then fault modeGen 2 installation manual |
The Lewmar 185TT GEN 2 Tunnel Thruster’s draw, cable, fuse, battery and run limit, as the maker publishes them.
- At 12 V: size the cable for your run, or check the battery you have.
The tunnel: length and depth rules
Tunnel length. A minimum suggested tunnel length of twice the diameter. Lewmar’s installation manual.
Depth below the waterline. One tunnel diameter below the waterline to keep air out of the tunnel, with 0.75 of a diameter the minimum. Gen 2 TT installation manual, 559231 Iss.3 (2018).
Our notes from the manual and listings
In the box: The solenoid, the ICU control box and a 2 m motor loom are in the box. The panel, its loom, the fuse and holder are bought.
3.0kW
Single propeller in a 185 mm tunnel with a stainless gearbox. This row covers four motors: 3.0, 4.0, 5.0 and 6.0 kW at 12 V. It is one Defender listing with a size menu and no part number shown until the option is chosen. The Gen 2 manual rates the 3.0 kW at 58 kgf (128 lb) and 20 kg.
It draws 330 A at 12 V behind a 250 A fuse. The cable is at least 95 mm² to 15 m of total run, battery to thruster and back. It rates the 6.0 kW at 97 kgf (214 lb), 27 kg, a 500 A fuse and 700 A on 300 mm² to 22 m.
Every fuse in the manual's table sits below the stated draw, and the 4.0 and 5.0 kW units draw ten amps apart for 17 kgf of difference. Lewmar's whole battery rule is that crank capacity should at least equal the thruster current. Run it in one direction for more than three minutes and the system enters fault mode.
A thermal switch stops a hot motor, and the manual says wait 20 minutes. The panel powers itself down after 15 minutes idle. The tunnel goes one diameter below the waterline (three quarters at minimum) and at least two diameters long. The anode is checked after three or four months on a new install, then yearly.
The manual says brush the carbon dust out of the motor, especially on an aluminum boat. Three years' warranty on paper, but one year on electric motors, associated electrical equipment and electronic controls. Service by anyone but an authorized Lewmar representative voids the warranty, and removal and reinstalling are not covered. Lewmar publishes no boat length.
Fisheries Supply's listings say 35 to 45 ft for the 3.0 kW, 40 to 55 for the 5.0, and two different bands for the 6.0 kW by voltage. The same part number is dearer at Fisheries Supply and dearer still at Lippert's own store. Defender's is the lowest of the three.
4.0kW
The 4.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 65 kgf (143 lb), 20 kg and a 400 A fuse. It gives 470 A at 12 V on at least 150 mm² cable to 16 m of total run. The 5.0 kW unit above it draws only ten amps more. Those are most of what fails on an electric thruster.
Lewmar publishes no boat length for any unit. Lippert's own store lists the same part number well above Defender.
5.0kW
The 5.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 82 kgf (181 lb), 27 kg, a 400 A fuse below its own 480 A at 12 V, on at least 185 mm² cable to 21 m of total run. Fisheries Supply's listing says 40 to 55 ft.
6.0kW
The 6.0 kW 185TT Gen 2, the biggest single-propeller Lewmar. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, a 500 A fuse below its own 700 A at 12 V, on at least 300 mm² cable to 22 m of total run, the biggest cable in the table. Fisheries Supply says 46 to 66 ft for this 12 V unit and 45 to 55 for the 24 V one, two bands for one motor.
6.0kW 24 V
The 6.0 kW 185TT Gen 2 at 24 V. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, with a 325 A fuse.
Where each point above comes from
- Lewmar sells it for either end, so it can go at the bow or the stern.The maker's listing
- The boat comes out of the water to install it: it needs a tunnel bore below the waterline.The mounting: a bore through the hull, or a housing recessed into it
- Lewmar prints no single length band for it. Its selection chart gives one by windage: 46 to 55 ft at 15 knots, across the kinds of boat in the table. The boat table is our sizing alone.Lewmar's Thruster Selection Guide, checked 15 September 2026
For the yard and the installer
Every published figure, with its source.
Full spec sheet
| Thrust and motor | |
|---|---|
| Thrust | 214 lb (97 kgf) As printed: Thrust: 214 lbs |
| Motor | 6 kW |
| Voltage | 12 V or 24 V |
| Run limit | 3 min in one direction, then fault mode |
| Installation | |
| Type | Tunnel, fixed mount |
| End of the boat | Bow or stern |
| Tunnel diameter | 185 mm |
| What it does to the hull | Tunnel bore below the waterline |
| Haul-out to install it | Yes |
| Maker’s boat length | 51 to 60 ftLewmar's selection chart, by windage; the listing prints none |
| Price and ordering | |
| Price | $3,427 to $4,825 equipment only, a dealer's price, defender.com, 26 October 2026 |
| Part number | 5900136.0kW 24 V, 24 V DC |
| Documents | |
| Manual | Installation manual (PDF)a dealer's copy (the maker publishes none we could find) |
| The site’s review | Lewmar thruster review |
Every published figure the site holds for the Lewmar 185TT GEN 2 Tunnel Thruster, with where each came from.
Draw, cable, fuse and battery at each voltage
These are the maker’s own figures, at each voltage it is sold at. The cable is the size for the shortest run in the maker’s table. A longer run may need heavier cable, and the wiring calculator works that out for your own boat.
| Voltage | Draw | Maker’s cable | Fuse | Battery | Run limit |
|---|---|---|---|---|---|
| 12 V | 700 Anominal draw | Over 2 x 4/0, past the common sizes, the one size Lewmar gives for this model, for any run up to 72 ft of cable counted out and backGen 2 installation manual, Iss.3 | 500 AGen 2 installation manual, Iss.3 | Crank capacity at least the 700 A draw, Lewmar's ruleLewmar Gen 2 installation manual | 3 min in one direction, then fault modeGen 2 installation manual |
| 24 V | 370 Anominal draw | 2 x 2/0 AWG per leg, the one size Lewmar gives for this model, for any run up to 59 ft of cable counted out and backGen 2 installation manual, Iss.3 | 325 AGen 2 installation manual, Iss.3 | Crank capacity at least the 370 A draw, Lewmar's ruleLewmar Gen 2 installation manual | 3 min in one direction, then fault modeGen 2 installation manual |
The Lewmar 185TT GEN 2 Tunnel Thruster’s draw, cable, fuse, battery and run limit, as the maker publishes them.
- At 12 V: size the cable for your run, or check the battery you have.
- At 24 V: size the cable for your run, or check the battery you have.
The tunnel: length and depth rules
Tunnel length. A minimum suggested tunnel length of twice the diameter. Lewmar’s installation manual.
Depth below the waterline. One tunnel diameter below the waterline to keep air out of the tunnel, with 0.75 of a diameter the minimum. Gen 2 TT installation manual, 559231 Iss.3 (2018).
Our notes from the manual and listings
In the box: The solenoid, the ICU control box and a 2 m motor loom are in the box. The panel, its loom, the fuse and holder are bought.
3.0kW
Single propeller in a 185 mm tunnel with a stainless gearbox. This row covers four motors: 3.0, 4.0, 5.0 and 6.0 kW at 12 V. It is one Defender listing with a size menu and no part number shown until the option is chosen. The Gen 2 manual rates the 3.0 kW at 58 kgf (128 lb) and 20 kg.
It draws 330 A at 12 V behind a 250 A fuse. The cable is at least 95 mm² to 15 m of total run, battery to thruster and back. It rates the 6.0 kW at 97 kgf (214 lb), 27 kg, a 500 A fuse and 700 A on 300 mm² to 22 m.
Every fuse in the manual's table sits below the stated draw, and the 4.0 and 5.0 kW units draw ten amps apart for 17 kgf of difference. Lewmar's whole battery rule is that crank capacity should at least equal the thruster current. Run it in one direction for more than three minutes and the system enters fault mode.
A thermal switch stops a hot motor, and the manual says wait 20 minutes. The panel powers itself down after 15 minutes idle. The tunnel goes one diameter below the waterline (three quarters at minimum) and at least two diameters long. The anode is checked after three or four months on a new install, then yearly.
The manual says brush the carbon dust out of the motor, especially on an aluminum boat. Three years' warranty on paper, but one year on electric motors, associated electrical equipment and electronic controls. Service by anyone but an authorized Lewmar representative voids the warranty, and removal and reinstalling are not covered. Lewmar publishes no boat length.
Fisheries Supply's listings say 35 to 45 ft for the 3.0 kW, 40 to 55 for the 5.0, and two different bands for the 6.0 kW by voltage. The same part number is dearer at Fisheries Supply and dearer still at Lippert's own store. Defender's is the lowest of the three.
4.0kW
The 4.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 65 kgf (143 lb), 20 kg and a 400 A fuse. It gives 470 A at 12 V on at least 150 mm² cable to 16 m of total run. The 5.0 kW unit above it draws only ten amps more. Those are most of what fails on an electric thruster.
Lewmar publishes no boat length for any unit. Lippert's own store lists the same part number well above Defender.
5.0kW
The 5.0 kW 185TT Gen 2, single propeller, stainless gearbox. The Gen 2 manual rates it 82 kgf (181 lb), 27 kg, a 400 A fuse below its own 480 A at 12 V, on at least 185 mm² cable to 21 m of total run. Fisheries Supply's listing says 40 to 55 ft.
6.0kW
The 6.0 kW 185TT Gen 2, the biggest single-propeller Lewmar. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, a 500 A fuse below its own 700 A at 12 V, on at least 300 mm² cable to 22 m of total run, the biggest cable in the table. Fisheries Supply says 46 to 66 ft for this 12 V unit and 45 to 55 for the 24 V one, two bands for one motor.
6.0kW 24 V
The 6.0 kW 185TT Gen 2 at 24 V. The Gen 2 manual rates it 97 kgf (214 lb), 27 kg, with a 325 A fuse.
Where each point above comes from
- Lewmar sells it for either end, so it can go at the bow or the stern.The maker's listing
- It is sold at 12 V and at 24 V.The maker's and dealers' listings
- The boat comes out of the water to install it: it needs a tunnel bore below the waterline.The mounting: a bore through the hull, or a housing recessed into it
- Lewmar prints no single length band for it. Its selection chart gives one by windage: 51 to 60 ft at 15 knots, across the kinds of boat in the table. The boat table is our sizing alone.Lewmar's Thruster Selection Guide, checked 15 September 2026
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