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Drawing of a tunnel thruster: a tube through the bow below the waterline, the hull cut away to show the motor on top. — Our drawing of a tunnel thruster, the same for every maker. It is not Lewmar’s own design.

Lewmar · tunnel thruster · bow or stern

Lewmar 300TT GEN 2: specs, price and the boats it fits

Name: Lewmar 300TT GEN 2 Tunnel Thruster
Brand: Lewmar

It gives 550 to 616 lb of push, across two sizes. Lewmar's own chart puts it on boats of 76 to 80 ft. It runs on 24 V or 48 V.

The unit$7,339 to $10,499Equipment only, Marinedeal, read 26 October 2026

Installed by a yard, 65 ft boat$16,106 to $30,307Our estimate: the unit, labor, haul-out, battery and parts

See it at Marinedeal$7,339 up How the installed cost adds up

Haul-out to install
DIY 2 of 5: wiring prep only
3-year warranty

Choose a size

The Lewmar 300TT GEN 2 Tunnel Thruster comes in two 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 two sizes

Every size of the Lewmar 300TT GEN 2 Tunnel Thruster
Size	Push	Voltage	Lewmar’s boat length	Price
300TT 10.8kW 24V	550 lb (249 kgf)	24 V	Not published	$7,339
300TT 15.0kW 48V	616 lb (279 kgf)	48 V	Not published	$10,499

From the database. The figures are Lewmar’s and the dealers’.

Quick stats

Thrust 550 lb 249 kgf, Lewmar's rating
Boat length 66 to 80 ft Lewmar's chart, by windage. See below
Price per lb of thrust $13.34 Unit only. $29 to $49 installed
Voltage 24 V As sold
Battery at 24 V 650 CCA Two batteries, 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 $52.32 A change, at Fisheries Supply

Quick stats

Thrust 616 lb 279 kgf, Lewmar's rating
Boat length 76 to 80 ft Lewmar's chart, by windage. See below
Price per lb of thrust $17.04 Unit only. $32 to $49 installed
Voltage 48 V As sold
Battery at 48 V 420 CCA Four batteries, 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 $52.32 A change, at Fisheries Supply

About the Lewmar 300TT GEN 2

The 300TT Gen 2 is Lewmar’s largest tunnel thruster: twin counter-rotating propellers in a 300 mm tube for the heaviest yachts Lewmar sizes for. Two motors are listed in the US, a 10.8 kW on 24 V and a 15.0 kW on 48 V, both with the bronze gearbox, giving 550 to 616 lb of push by the Gen 2 manual.

Marinedeal is the only US store we found that lists them, at $7,339 for the 24 V and $10,499 for the 48 V. Its part numbers do not match the manual’s, and its product codes are the Gen 1 numbers, so confirm the build with the dealer before you pay. The manual gives the 24 V unit a 500 A fuse and the 48 V one 400 A. See every part.

A thruster this size needs its own battery bank near the bow, which is the biggest cost after the unit. The Gen 2 rules apply: three minutes one way and the system goes into fault mode. The warranty limits motors and electronic controls to one year.

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 (5 sources, read 15 October 2026)

Will the Lewmar 300TT GEN 2 Tunnel Thruster steer your boat?

80 FT TRAWLER · BOW · 15 KT WIND

Size forThis page always opens on Steering.

Every knot figure here is wind speed, not boat speed or current.

Steers her at 17 kt

On a 80 ft trawler the Lewmar 300TT GEN 2 Tunnel Thruster (550 lb) steers her in a 17 knot breeze. Her bow needs about 428 lb from a tunnel to steer her in a 15 knot breeze.

The finder lists it for her.

A tunnel at the bow of a 80 ft trawler 428 lb ★ this unit · 1 to 3: the three cheapest others that steer her at 13 kt or more, installed

★ Lewmar 300TT GEN 2 Tunnel Thruster this unit 550 lb · tunnel from $16,356 Steers her at 17 kt
1 Max Power CT225 (composite leg) 551 lb · tunnel from $13,257 Steers her at 17 kt
2 Max Power CT325 (24 V) 717 lb · tunnel from $16,407 Steers her at 19 kt
3 VETUS Bow 220 485 lb · tunnel from $16,514 Steers her at 16 kt

The Lewmar 300TT GEN 2 Tunnel Thruster on a trawler, by length

25 ft54 kt
30 ft45 kt
35 ft39 kt
40 ft34 kt
45 ft30 kt
50 ft27 kt
55 ft25 kt
60 ft23 kt
65 ft21 kt
70 ft19 kt
75 ft18 kt
80 ft17 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?

What Lewmar says Not in the listing Lewmar gives its range on its chart, next to this

What Lewmar’s chart says 66 to 80 ft As the 300TT 10.8, the tunnel with this thrust, in 11 to 16 knots.

What our sizing says 70 to 80 ft Full thrust in 15 knots, across the kinds of boat it fits

Every kind of boat it fits, by length ten boat types

Which boats 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	65 to 80 ft	None	71 to 80 ftas the 300TT 10.8, class B
Houseboat	49 to 70 ft	71 to 80 ftfull thrust to about 13 knots at 80 ft	66 to 75 ftas the 300TT 10.8, class C
Catamaran	74 to 80 ft	None	66 to 75 ftas the 300TT 10.8, class C
Trawler	65 to 80 ft	None	66 to 75 ftas the 300TT 10.8, class C
Motor yacht	65 to 80 ft	None	66 to 75 ftas the 300TT 10.8, 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	No length. More thrust than the boat needs.
Center console	No length. More thrust than the boat needs.

The Lewmar 300TT 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 70 ft, and a sailboat to 80 ft.

The table tries the Lewmar 300TT 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 class and a wind band. Our 15 knots falls in its lightest band, 11 to 16 knots.

The Lewmar 300TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 550 lb (249 kgf) as the 300TT 10.8. 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 five 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.

Installed by a yard
Boat	Total installed
49 ft	$15,836 to $25,913$29 to $47 a lb of thrust
65 ft	$16,106 to $26,693$29 to $49 a lb of thrust
80 ft	$16,356 to $27,413$30 to $50 a lb of thrust

From the shortest to the longest boat it is sized for.

What is in each total five lines

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 adds $970 to $3,860 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.

Each line of the estimate
Boat length	The unit	Yard labor	Haul-out	Batteries, cable, charger	Other parts
49 ft	$7,339	$5,120 to $12,60032 to 70 hours	$970 to $2,360	$1,226 to $1,495	$1,181 to $2,119
65 ft	$7,339	$5,120 to $12,60032 to 70 hours	$1,240 to $3,140	$1,226 to $1,495	$1,181 to $2,119
80 ft	$7,339	$5,120 to $12,60032 to 70 hours	$1,490 to $3,860	$1,226 to $1,495	$1,181 to $2,119

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 24 V: two 12 V batteries in series, at least 650 CCA each (Lewmar’s minimum), $720 for both; 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.

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 2 of 5: Wiring prep only. The yard installs the unit and does the hull work; you do the wiring prep.

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 DIY

You: 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 three steps

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 300TT GEN 2 Tunnel Thruster steer your boat?

80 FT TRAWLER · BOW · 15 KT WIND

Size forThis page always opens on Steering.

Every knot figure here is wind speed, not boat speed or current.

Steers her at 18 kt

On a 80 ft trawler the Lewmar 300TT GEN 2 Tunnel Thruster (616 lb) steers her in an 18 knot breeze. Her bow needs about 428 lb from a tunnel to steer her in a 15 knot breeze.

The finder leaves it off her list. It shows the 300TT 10.8kW 24V for her instead.

A tunnel at the bow of a 80 ft trawler 428 lb ★ this unit · 1 to 3: the three cheapest others that steer her at 13 kt or more, installed

★ Lewmar 300TT GEN 2 Tunnel Thruster this unit 616 lb · tunnel from $19,970 Steers her at 18 kt
1 Max Power CT225 (composite leg) 551 lb · tunnel from $13,257 Steers her at 17 kt
2 Max Power CT325 (24 V) 717 lb · tunnel from $16,407 Steers her at 19 kt
3 VETUS Bow 220 485 lb · tunnel from $16,514 Steers her at 16 kt

The Lewmar 300TT GEN 2 Tunnel Thruster on a trawler, by length

25 ft57 kt
30 ft48 kt
35 ft41 kt
40 ft36 kt
45 ft32 kt
50 ft29 kt
55 ft26 kt
60 ft24 kt
65 ft22 kt
70 ft21 kt
75 ft19 kt
80 ft18 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?

What Lewmar says Not in the listing Lewmar gives its range on its chart, next to this

What Lewmar’s chart says 76 to 80 ft As the 300TT 15.0, the tunnel with this thrust, in 11 to 16 knots.

What our sizing says 74 to 80 ft Full thrust in 15 knots, across the kinds of boat it fits

Every kind of boat it fits, by length ten boat types

Which boats 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	69 to 80 ft	None	Off the chart
Houseboat	52 to 74 ft	75 to 80 ftfull thrust to about 14 knots at 80 ft	76 to 80 ftas the 300TT 15.0, class C
Catamaran	79 to 80 ft	None	76 to 80 ftas the 300TT 15.0, class C
Trawler	69 to 80 ft	None	76 to 80 ftas the 300TT 15.0, class C
Motor yacht	69 to 80 ft	None	76 to 80 ftas the 300TT 15.0, 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	No length. More thrust than the boat needs.
Center console	No length. More thrust than the boat needs.

The Lewmar 300TT 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.

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 74 ft, and a sailboat to 80 ft.

The Lewmar 300TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 616 lb (279 kgf) as the 300TT 15.0. 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 five 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.

Installed by a yard
Boat	Total installed
52 ft	$19,500 to $29,677$32 to $48 a lb of thrust
65 ft	$19,720 to $30,307$32 to $49 a lb of thrust
80 ft	$19,970 to $31,027$32 to $50 a lb of thrust

From the shortest to the longest boat it is sized for.

What is in each total five lines

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 adds $1,020 to $3,860 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.

Each line of the estimate
Boat length	The unit	Yard labor	Haul-out	Batteries, cable, charger	Other parts
52 ft	$10,499	$5,120 to $12,60032 to 70 hours	$1,020 to $2,510	$1,680 to $1,949	$1,181 to $2,119
65 ft	$10,499	$5,120 to $12,60032 to 70 hours	$1,240 to $3,140	$1,680 to $1,949	$1,181 to $2,119
80 ft	$10,499	$5,120 to $12,60032 to 70 hours	$1,490 to $3,860	$1,680 to $1,949	$1,181 to $2,119

For every length in the table above.

Batteries and lugs are priced at Fisheries Supply and the cable and charger at Defender, read 26 October 2026.

At 48 V: four 12 V batteries in series, at least 420 CCA each (Lewmar’s minimum), $1,027 for all four; 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; two GEN5X2 chargers, $293.

DIY breakdown

DIY 2 of 5: Wiring prep only. The yard installs the unit and does the hull work; you do the wiring prep.

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 DIY

You: 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 three steps

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.

Know before you buy

What sets this model apart, what it costs to keep, and what to weigh.

Price per pound of thrust

$13.34 a lb

250TT GEN 2, 308 lb $16.07
300TT GEN 2, 550 lb $13.34
VETUS Bow 285, 628 lb $13.31
Quick BTQ 300, 551 lb $21.71
Sleipner SE250/300TC, 661 lb $13.34

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

$52.32 a change

Anode kit (589550): $52.32 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 24 V it wants two batteries of 650 CCA or more, Lewmar's figure. The cheapest that meets it is the Optima BlueTop SC27DM Group 27 AGM, $359.99. 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: 76 to 80 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.

Parts for the Lewmar 300TT GEN 2 Tunnel Thruster

See the Lewmar 300TT GEN 2 manual

Search 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.

Find a part

For the install what the box leaves you to buy

15 parts

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, $1,181 to $2,119 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 “Sleipner fiberglass tunnel tube, 300 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. No Lewmar tube is listed at this bore. This one is another maker's.

Part number SM13010

See it at Fisheries Supply$852.47 Price read 26 Oct 2026

Control panel

Fisheries Supply lists it as “Lewmar Gen 2 single joystick control”.

Check the listing or the box before you buy: the maker does not say whether one is included.

Part number 589268

See it at Fisheries Supply$373.53 Price read 26 Oct 2026

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.

Part number 589802

See it at Fisheries Supply$69.10 Price read 26 Oct 2026

Main fuse

Ask for 500 A (Lewmar 589011). This one is for the 10.8kW 24 V, bronze gearbox version.

Lewmar's figure for the 590034, TT 300 10.8 24v (bronze) (Gen 2 installation manual, Iss.3). Not listed at Fisheries Supply; ask a Lewmar dealer.

Part number See the line above.

See it in the Lewmar manual No US price found

Main fuse

Ask for 400 A (Lewmar 589010). This one is for the 15.0kW 48 V, bronze gearbox version.

Lewmar's figure for the 590035, TT 300 15.0 48v (Gen 2 installation manual, Iss.3). Not listed at Fisheries Supply; ask a Lewmar dealer.

Part number See the line above.

See it in the Lewmar manual No US price found

Fuse holder

Ask for Lewmar fuse holder 589013 (T2).

Ask the dealer who sells the fuse.

Part number See the line above.

See it in the Lewmar manual No US price found

Battery switch

Fisheries Supply lists it as “HD-Series 600 A battery switch, on/off”. This one is for the 10.8kW 24 V, bronze gearbox version.

Rated at or above the 500 A main fuse. If your manual names its own switch, use that one.

Part number 3000

See it at Fisheries Supply$107.18 Price read 26 Oct 2026

Battery switch

Fisheries Supply lists it as “HD-Series 600 A battery switch, on/off”. This one is for the 15.0kW 48 V, bronze gearbox version.

Rated at or above the 400 A main fuse. If your manual names its own switch, use that one.

Part number 3000

See it at Fisheries Supply$107.18 Price read 26 Oct 2026

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.

Part number 5065

See it at Fisheries Supply$11.52 Price read 26 Oct 2026

Batteries

Fisheries Supply lists it as “Optima BlueTop SC27DM Group 27 AGM”. This one is for the 10.8kW 24 V, bronze gearbox version.

You need 2, each at 650 CCA or more, in series for 24 V. The cheapest listing that meets it.

Part number BAT SC27DM

See it at Fisheries Supply$359.99 Price read 26 Oct 2026

Batteries

Fisheries Supply lists it as “Lifeline GPL-1400T AGM starting”. This one is for the 15.0kW 48 V, bronze gearbox version.

You need 4, each at 420 CCA or more, in series for 48 V. The cheapest listing that meets it.

Part number LFL GPL-1400T

See it at Fisheries Supply$256.72 Price read 26 Oct 2026

Battery cable, red and black

Defender lists it as “Ancor tinned battery cable 4/0 AWG, cut to length, red or black”.

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.

Part number None on the listing. Order it by name.

See it at Defender$13.25 a foot Price read 26 Oct 2026

Cable lugs

Fisheries Supply lists it as “Tin-plated starter lugs, 4/0 AWG, bag of 10”.

You need 2 bags. The listing runs $47.52 to $49.44 by stud size. Eight ends on one run, with two spare.

Part number 91066-P10

See it at Fisheries Supply$47.52 Price read 26 Oct 2026

Charger

Fisheries Supply lists it as “GEN5X2 on-board charger, 10 A, 2 banks”. This one is for the 10.8kW 24 V, bronze gearbox version.

Or a DC-to-DC charger from the house system: ask the electrician.

Part number GEN5X2

See it at Fisheries Supply$146.41 Price read 26 Oct 2026

Charger

Fisheries Supply lists it as “GEN5X2 on-board charger, 10 A, 2 banks”. This one is for the 15.0kW 48 V, bronze gearbox version.

You need 2. Or a DC-to-DC charger from the house system: ask the electrician.

Part number GEN5X2

See it at Fisheries Supply$146.41 Price read 26 Oct 2026

Outside the hull replacement parts in the water

5 parts

Anode kit

The metal that wears away in the water so the drive does not. Lewmar calls it “Anode kit, 250TT and 300TT”.

Fisheries Supply lists it as a pair.

Part number 589550

See it at Fisheries Supply$52.32 Price read 29 Oct 2026

Propeller washer

The propeller on the drive. Lewmar calls it “PLASTIC WASHER”.

Part number 555038

See it in the Lewmar manual No US price found

Propeller, left hand

The propeller on the drive. Lewmar calls it “LH PROPELLER & WASHER”.

The 300TT runs two counter-rotating propellers. Order the right and left hand separately.

Part number 589751

See it at Fisheries Supply$231.96 Price read 29 Oct 2026

Propeller, right hand

The propeller on the drive. Lewmar calls it “RH PROPELLER & WASHER”.

The 300TT runs two counter-rotating propellers. Order the right and left hand separately.

Part number 589750

See it at Fisheries Supply$231.96 Price read 29 Oct 2026

Tunnel gasket

It keeps water out of the joint it sits in. Lewmar calls it “TUNNEL GASKET”.

Part number 557035

See it in the Lewmar manual No US price found

Inside the boat replacement parts on board

11 parts

Solenoid (the motor switch)

The heavy switch that sends battery power to the motor. Lewmar calls it “SOLENOID 10.8KW”. This one is for the 10.8 kW 24 V version. It fits the 10.8kW 24V, bronze gearbox size on this page.

Part number B8429

See it in the Lewmar manual No US price found

Solenoid (the motor switch)

The heavy switch that sends battery power to the motor. Lewmar calls it “SOLENOID 15KW”. This one is for the 15.0 kW 48 V version. It fits the 15.0kW 48V, bronze gearbox size on this page.

Part number B11762

See it in the Lewmar manual No US price found

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.

Part number 589274

See it at Defender$167.99 Price read 29 Oct 2026

See it at Fisheries Supply$197.66 Price read 24 Oct 2026

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 15.0kW 48V, bronze gearbox size 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).

Part number 589010

See it in the Lewmar manual No US price found

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 10.8kW 24V, bronze gearbox 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.

Part number 589011

See it at West Marine$48.95 Price read 24 Oct 2026

Control panel, dual joystick (bow and stern)

The control at the helm. Lewmar calls it “Controller, Dual Joystick”.

Part number 589267

See it at Fisheries Supply$665.05 Price read 29 Oct 2026

Control panel, dual pad (bow and stern)

The control at the helm. Lewmar calls it “Controller, Dual Pad”.

Part number 589222

See it at Defender$292.99 Price read 29 Oct 2026

Control panel, single joystick

The control at the helm. Lewmar calls it “Controller, Single Joystick”.

Part number 589268

See it at Fisheries Supply$373.53 Price read 29 Oct 2026

Control panel, single pad

The control at the helm. Lewmar calls it “Controller, Single Pad”.

Part number 589223

See it at Fisheries Supply$313.07 Price read 29 Oct 2026

Replacement motor

The electric motor that turns the propeller. Lewmar calls it “MOTOR ASSY 10.8KW 24V”. This one is for the 10.8 kW 24 V version. It fits the 10.8kW 24V, bronze gearbox size on this page.

Part number 587032

See it in the Lewmar manual No US price found

Replacement motor

The electric motor that turns the propeller. Lewmar calls it “MOTOR ASSY 15KW 48V”. This one is for the 15.0 kW 48 V version. It fits the 15.0kW 48V, bronze gearbox size on this page.

Part number 557030

See it in the Lewmar manual No US price found

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

Compare them side by side

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, motor, mounting, price, part number, documents

Full spec sheet
Thrust and motor
Thrust	550 lb (249 kgf) As printed: "590034 TT 300 10.8 24v 300 10.8 14.5 24v Bronze Twin CR 5 Blade 250 550 65 143 500A 589011" - Lewmar Gen 2 TT manual 559231 Iss.3, section 6
Motor	10.8 kW
Voltage	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	300 mm
What it does to the hull	Tunnel bore below the waterline
Haul-out to install it	Yes
Maker’s boat length	66 to 80 ftLewmar's selection chart, by windage; the listing prints none
Price and ordering
Price	$7,339 equipment only, a dealer's price, marinedeal.com, 26 October 2026
Part number	59003410.8kW 24 V, bronze gearbox, 24 V DC 59003515.0kW 48 V, bronze gearbox, 48 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 300TT GEN 2 Tunnel Thruster, with where each came from.

Draw, cable, fuse and battery at each voltage 24 V

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.

Draw, cable, fuse and battery
Voltage	Draw	Maker’s cable	Fuse	Battery	Run limit
24 V	650 Anominal draw	Over 2 x 4/0, past the common sizes, the one size Lewmar gives for this model, for any run up to 82 ft of cable counted out and backGen 2 installation manual, Iss.3	400 A or 500 AGen 2 installation manual, Iss.3	Crank capacity at least the 650 A draw, Lewmar's ruleLewmar Gen 2 installation manual	3 min in one direction, then fault modeGen 2 installation manual

The Lewmar 300TT GEN 2 Tunnel Thruster’s draw, cable, fuse, battery and run limit, as the maker publishes them.

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.

10.8kW 24 V, bronze gearbox

The 300TT Gen 2 at 10.8 kW and 24 V: twin counter-rotating propellers in a 300 mm tunnel. The Gen 2 manual rates it 250 kgf (550 lb), 65 kg, with a 500 A fuse.

15.0kW 48 V, bronze gearbox

The 300TT Gen 2 at 15.0 kW and 48 V. The Gen 2 manual rates it 280 kgf (616 lb), 68 kg, with a 400 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: 66 to 80 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, motor, mounting, price, part number, documents

Full spec sheet
Thrust and motor
Thrust	616 lb (279 kgf) As printed: "590035 TT 300 15.0 48v 300 15.0 20.0 48v Bronze Twin CR 5 Blade 280 616 68 150 400A 589010" - Lewmar Gen 2 TT manual 559231 Iss.3, section 6
Motor	15 kW
Voltage	48 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	300 mm
What it does to the hull	Tunnel bore below the waterline
Haul-out to install it	Yes
Maker’s boat length	76 to 80 ftLewmar's selection chart, by windage; the listing prints none
Price and ordering
Price	$10,499 equipment only, a dealer's price, marinedeal.com, 26 October 2026
Part number	59003410.8kW 24 V, bronze gearbox, 24 V DC 59003515.0kW 48 V, bronze gearbox, 48 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 300TT GEN 2 Tunnel Thruster, with where each came from.

Draw, cable, fuse and battery at each voltage 48 V

Draw, cable, fuse and battery
Voltage	Draw	Maker’s cable	Fuse	Battery	Run limit
48 V	420 Anominal draw	2 x 3/0 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	400 AGen 2 installation manual, Iss.3	Crank capacity at least the 420 A draw, Lewmar's ruleLewmar Gen 2 installation manual	3 min in one direction, then fault modeGen 2 installation manual

The Lewmar 300TT GEN 2 Tunnel Thruster’s draw, cable, fuse, battery and run limit, as the maker publishes them.

At 48 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.

10.8kW 24 V, bronze gearbox

The 300TT Gen 2 at 10.8 kW and 24 V: twin counter-rotating propellers in a 300 mm tunnel. The Gen 2 manual rates it 250 kgf (550 lb), 65 kg, with a 500 A fuse.

15.0kW 48 V, bronze gearbox

The 300TT Gen 2 at 15.0 kW and 48 V. The Gen 2 manual rates it 280 kgf (616 lb), 68 kg, with a 400 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: 76 to 80 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

Not sure this is the one? The thruster finder asks about your boat and prices every unit that fits.

Where to go next

Which thruster does your boat need? Seven to nine questions: the thrusters that fit your boat, with costs.
Compare thrusters side by side Pick up to four tunnel, retractable or external units and see specs, price and fit together.
Lewmar thruster review The chandlery-shelf range: the warranty’s fine print, run time, three store prices, owner reports.

The specs are the maker’s and the dealers’, on the dates shown. The sizing and the costs are our arithmetic, done without seeing your boat.

Lewmar 300TT GEN 2: specs, price and the boats it fits

Choose a size

Quick stats

Quick stats

About the Lewmar 300TT GEN 2

Will the Lewmar 300TT GEN 2 Tunnel Thruster steer your boat?

Is it right for your boat?

What it costs installed

DIY breakdown

Will the Lewmar 300TT GEN 2 Tunnel Thruster steer your boat?

Is it right for your boat?

What it costs installed

DIY breakdown

Related videos

Know before you buy

Price per pound of thrust

Controls

Anodes

Service and warranty

Special mentions

What to weigh

Parts for the Lewmar 300TT GEN 2 Tunnel Thruster

For the install what the box leaves you to buy

Tunnel tube

Control panel

Control cable, panel to thruster

Main fuse

Main fuse

Fuse holder

Battery switch

Battery switch

Control-circuit fuse holder

Batteries

Batteries

Battery cable, red and black

Cable lugs

Charger

Charger

Outside the hull replacement parts in the water

Anode kit

Propeller washer

Propeller, left hand

Propeller, right hand

Tunnel gasket

Inside the boat replacement parts on board

Solenoid (the motor switch)

Solenoid (the motor switch)

Controller box (the ICU)

Main fuse, 400 A

Main fuse, 500 A

Control panel, dual joystick (bow and stern)

Control panel, dual pad (bow and stern)

Control panel, single joystick

Control panel, single pad

Replacement motor

Replacement motor

Other sizes and close alternatives

For the yard and the installer

10.8kW 24 V, bronze gearbox

15.0kW 48 V, bronze gearbox

For the yard and the installer

10.8kW 24 V, bronze gearbox

15.0kW 48 V, bronze gearbox

Where to go next