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Sleipner · tunnel thruster · bow or stern
Sleipner SE30/125S DC: specs, price and the boats it fits
It gives 88 lb (40 kgf) of push. Sleipner sells it for boats of 20 to 28 ft. It runs on 12 V.
- Haul-out to install
- DIY 2 of 5: wiring prep only
- 2-year warranty
Quick stats
- Thrust 88 lb 40 kgf, Sleipner's rating
- Boat length 20 to 28 ft Sleipner's own range
- Price per lb of thrust $19.94 Unit only. $95 to $120 installed
- Voltage 12 V As sold
- Battery at 12 V 380 CCA One battery, near the thruster
- Run limit 2 to 3 min Duty cycle at 20 C ambient
- To install it Haul-out The boat comes out of the water
- Anodes $9.00 A change, at Defender
About the Sleipner SE30/125S DC
The SE30 is a small, affordable bow thruster for boats of about 20 to 28 ft, the size where one gust at the dock can undo a good approach. It delivers 88 lb of push on 12 V from a short tube near the bow. Sleipner has built in Fredrikstad, Norway, since 1910, and sold its thrusters as Side-Power until 2021.
At $1,755 from Defender, it is one of the least costly ways into a proper tunnel thruster. Plan on about $473 to $1,024 more for the tube, a helm panel, a main switch and a fuse. It wants a starting (cranking) battery with short cables to it, and we estimate $498 to $574 for that battery, cable and charging. See every part.
Read more
It is a plain on/off unit, which owners like for its simplicity. Give it short pushes: Sleipner’s page rates the motor for 2 to 3 minutes at a time. Owners say the plastic propeller gives way before the drive if a line gets caught, and a new one is inexpensive. Two years of warranty, and it stays with the boat when you sell.
Installers will find the wiring figures and dimensions further down. For the rest of Sleipner’s line, read the Sleipner (Side-Power) review.
Sleipner sold its thrusters under the Side-Power name until 2021, and many dealers and owners still call them that. It is the same company and the same thrusters.
Where this summary comes from (5 sources, read 12 October 2026)
- Sleipner product page
- Sleipner FAQ (rated voltage, the Sleipner name since 2021, batteries and lithium, tunnel depth)
- Sleipner: this is Sleipner (company history, Fredrikstad since 1908)
- Sleipner warranty statement, effective 1 April 2022
- Trawler Forum, "Bow thruster manufacturer opinions", Dec 2021 (ten years on two Side-Power units; the prop built to break)
Will the Sleipner SE30/125S DC steer your boat?
30 FT TRAWLER · BOW · 15 KT WIND
Every knot figure here is wind speed, not boat speed or current.
On a 30 ft trawler the Sleipner SE30/125S DC (88 lb) steers her in an 18 knot breeze. Her bow needs about 60 lb from a tunnel to steer her in a 15 knot breeze.
The finder lists it for her.
The Sleipner SE30/125S DC on a trawler, by length
- 25 ft22 kt
- 30 ft18 kt
- 35 ft15 kt
- 40 ft14 kt
- 45 ft12 kt
- 50 ft11 kt
- 55 ft10 kt
- 60 ft9 kt
- 65 ft8 kt
- 70 ft8 kt
- 75 ft7 kt
- 80 ft7 kt
Outlined: the finder does not list it at that length (under 13 kt, far more than she needs, or outside Sleipner’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 |
|---|---|---|
| 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 | 26 to 30 ft | None |
| Houseboat | None | 30 ft onlyfull thrust to about 14 knots at 30 ft |
| Catamaran | 30 ft only | None |
| Trawler | 26 to 30 ft | None |
| Motor yacht | No length. Outside the maker's length range. | |
| 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 Sleipner SE30/125S DC against each kind of boat, in a 15 knot wind. Our sizing, from the finder’s own rules.
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 every kind of boat it fits gets full thrust to 30 ft. The maker gives one range for every boat.
The table tries the Sleipner SE30/125S DC 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 and the maker lists it for that length.
A boat up to 10 percent past the maker’s range still counts here, as it does in the finder. So the table runs up to 30 ft, just past Sleipner’s own range (20 to 28 ft).
It is sized for four 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 |
|---|---|
| 26 ft | $8,306 to $10,363$94 to $118 a lb of thrust |
| 30 ft | $8,386 to $10,563$95 to $120 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 $460 to $1,450 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 |
|---|---|---|---|---|---|
| 26 ft | $1,755 | $5,120 to $5,760about 32 hours | $460 to $1,250 | $498 to $574 | $473 to $1,024 |
| 30 ft | $1,755 | $5,120 to $5,760about 32 hours | $540 to $1,450 | $498 to $574 | $473 to $1,024 |
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 380 CCA (Sleipner’s minimum), $257 for the battery; Sleipner’s cable table gives 1/0 AWG: $95 to $171 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 Sleipner’s own channel and one 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
$19.94 a lb The unit’s price over its published thrust. The bars are Sleipner’s next sizes and the nearest other makers.Controls
Gasket, bolts and anode with the unit. The panel, its cable, the fuse and main switch are bought.
- Side-Power 8950 G touch panel, one thruster (SM8950G), $219.21 at Fisheries Supply.
- Side-Power 4-lead control cable, 4 m (SM61277-04M), $29.23 at Fisheries Supply.
Anodes
$9.00 a change- Anode (SM31180A): $9.00 at Defender, $11.25 at Fisheries Supply.
They sit below the waterline, so a change means a haul-out or a diver.
Service and warranty
Sleipner gives 2 years for leisure use and 1 for commercial use. It transfers to the next owner, and it starts no later than 18 months after the boat's first launch.
See Sleipner’s warranty Sleipner's warranty statement, effective 1 April 2022.Special mentions
Battery: at 12 V it wants one battery of 380 CCA or more, Sleipner'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.
Gas engine room? Buy the ignition-protected Sleipner SE30/125S-IP, $3,195.
Sleipner 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.
Short pushes only: Sleipner rates the motor for 2 to 3 min at a stretch.
Parts for the Sleipner SE30/125S DC
See the Sleipner SE30/125S DC manualThe US dealer number comes first, then Sleipner’s own. 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 on the maker's product page. It has the hull, wiring and fuse figures for this model.
From Sleipner’s SE20 to SE40 installation guide, document 5611 rev 25, 2025, read 25 October 2026.
- In the box
- The guide prints no box list. It has you install the unit with the gasket and the bolts provided.
- Bought separately
- The ANL fuse and a main switch ("must include"), the control panel with its own guide, the panel cable, the tunnel and the cable. Imtra, Sleipner's US distributor, lists the same items to buy with a new thruster.
- Charging
- The word "charging" is not in any of the Sleipner guides we read. The battery is sized by cold cranking amps, and a battery near the thruster is suggested. How it gets charged is left to you and your installer.
In Sleipner’s words, from its SE80 to SE150 installation guide, document 2687 rev 30, page 19: “For installations on large vessels with bow and stern thrusters or catamarans a dedicated battery for each thruster should be considered.”
The “other parts” line in the estimate above covers these parts as a range, $473 to $1,024 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, 125 mm bore, 600 mm”.
Sold in lengths from about 24 to 35 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 “Side-Power 8950 G touch panel, one thruster”.
Control cable, panel to thruster
Fisheries Supply lists it as “Side-Power 4-lead control cable, 4 m”.
Sold in lengths from 4 to 22 m. This is the shortest: measure the run from the helm to the thruster and buy the length that reaches.
Main fuse
Fisheries Supply lists it as “Side-Power ANL fuse 150 A”.
The maker's figure: ANL 150.
Fuse holder
Fisheries Supply lists it as “ANL compact fuse block, 35 to 300 A, cable up to 2/0, with cover”.
Battery switch
Fisheries Supply lists it as “m-Series 300 A battery switch, on/off”.
Rated at or above the 150 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”.
Your manual names no value for this: size a small in-line fuse to the wire.
Batteries
Fisheries Supply lists it as “Lifeline GPL-1400T AGM starting”.
One at 380 CCA or more. The cheapest listing that meets it.
Battery cable, red and black
Defender lists it as “Ancor tinned battery cable 1/0 AWG, cut to length, red or black”.
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.
Cable lugs
Fisheries Supply lists it as “Tin-plated starter lugs, 1/0 AWG, bag of 10”.
The listing runs $23.74 to $28.04 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
The metal that wears away in the water so the drive does not. Sleipner calls it “Anode, aluminium SE20/25/30/40/50”.
Sleipner lists it on the SE40 page and on the gear leg pages for the 110, 125 and 140 mm SE units (gear legs 2 0600, 3 0601, 5 0600).
Propeller
The propeller on the drive. Sleipner calls it “Propeller SE30/40 5bl Q-Prop™”.
For the 125 mm tunnel (gear leg 3 0601). An SE30 or SE40 in a 140 mm tunnel takes a different propeller, SM150937.
Drive pin (the pin that drives the propeller)
The pin that locks the propeller to its shaft. Sleipner calls it “Drive pin SE30/40 + SP30/35”.
Sleipner's page lists no models; only the name covers the SE30 and SE40.
Gear leg, with propeller
The leg under the motor that turns the propeller. Sleipner calls it “Gearleg SE30/40”.
The 125 mm gear leg. The 140 mm version is SM152675.
Inside the boat replacement parts on board
Shear pin (breaks to protect the drive)
A pin made to break if the propeller hits something, so the drive does not. Sleipner calls it “Shear pin 4mm SP30/35/40/SE30/40”.
Sleipner's page lists no models; only the name covers the SE30 and SE40. Confirm with your serial number.
Motor brush kit
Carbon brushes inside the motor. They wear down with use. Sleipner calls it “Brush kit SE25/30 + SP30”. This one is for the serial #700161 and above version.
Sleipner asks for the thruster's serial number with every brush kit order. More than one kit is in print for this model, and the serial number decides which.
Motor brush kit
Carbon brushes inside the motor. They wear down with use. Sleipner calls it “Brush kit SE25/30/40”. This one is for the serial #U version.
Sleipner asks for the thruster's serial number with every brush kit order. More than one kit is in print for this model, and the serial number decides which.
Controller (the relay box on the motor)
A small switch in the motor’s control circuit. Sleipner calls it “Controller SE25/30 12V”.
Listed on the SE30 12 V motor page.
Solenoid (the motor switch)
The heavy switch that sends battery power to the motor. Sleipner calls it “Solenoid SE20/25/30”.
Listed on Sleipner's SE30 12 V motor page (2 0101 12).
Main fuse
The main fuse at the battery, in the rating the maker gives. Sleipner calls it “Recommended fuse A”.
The rating on Sleipner's product page for this model.
Control panel, on/off dual joystick (bow and stern)
The control at the helm. Sleipner calls it “Dual joystick, 12/24 V”.
Runs a bow and a stern thruster.
Control panel, on/off single joystick
The control at the helm. Sleipner calls it “Single joystick, 12/24 V”.
For one on/off thruster.
Control panel, on/off touch panel
The control at the helm. Sleipner calls it “Touch panel, 12/24 V, 5-wire, round cut-out”.
For one on/off thruster.
Replacement motor
The electric motor that turns the propeller. Sleipner calls it “Electric motor SE30 12V”.
No part matches. Try the number without spaces, or the part’s name.
The install parts are matched to Sleipner’s own figures and priced at Fisheries Supply, with the battery cable at Defender, cut to length.
Spare part numbers come from Sleipner’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 Sleipner SE25/110S 66 lb · $1,485
- Size up Sleipner SE40/125S 105 lb · $1,845
- Ignition-protected Sleipner SE30/125S-IP 88 lb · $3,195
- Other maker Max Power CT45-IP 88 lb · $2,456
- Other maker Quick BTQ 125 two sizes, 66 to 88 lb · $2,511 to $2,754
- Other maker Lewmar 140TT Gen 2 Package 92 lb · $2,754
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 | 88 lb (40 kgf) As printed: Thrust at 12V: 40kg / 88lbs; Thrust at 10.5V: 30kg / 66lbs |
| Thrust under load | 66 lb at 10.5 V |
| Motor | 1.5 kW |
| Voltage | 12 V |
| Run limit | 2 to 3 min duty cycle at 20 C ambient |
| Installation | |
| Type | Tunnel, fixed mount |
| End of the boat | Bow or stern |
| Tunnel diameter | 125 mm |
| What it does to the hull | Tunnel bore below the waterline |
| Haul-out to install it | Yes |
| Maker’s boat length | 20 to 28 ft |
| Price and ordering | |
| Price | $1,755 equipment only, a dealer's price, defender.com, 26 October 2026 |
| Part number | Not held for this listing |
| Documents | |
| Manual | Installation manualon the maker's product page |
| The site’s review | Sleipner (Side-Power) review |
Every published figure the site holds for the Sleipner SE30/125S DC, 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 | 245 Anominal draw | 1/0 AWG for up to 22 ft of cable counted out and back. Longer runs take heavier cableinstallation guide | ANL 150installation guide | 200 CCA DIN minimumSleipner installation manual, SE30/125S | 2 to 3 min duty cycle at 20 C ambientproduct page, "Motor cycle duty" |
The Sleipner SE30/125S DC’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. Avoid a tunnel longer than four times its diameter. Friction inside a long tube slows the water and cuts thrust. Too short, and the flow reaches the propeller before it has straightened, which the manual says causes cavitation and noise. The propeller must sit entirely inside the tube. Sleipner’s installation manual.
Depth below the waterline. As deep as possible under the waterline, and as far forward as possible. The depth for a given model is in that model’s own measurements. Deeper prevents air being sucked in from the surface and raises the water pressure at the propeller. SE20 to SE40 installation guide, 5611 rev 25 (2025).
Our notes from the manual and listings
In the box: Gasket, bolts and anode with the unit. The panel, its cable, the fuse and main switch are bought.
Our note
A 125 mm tunnel for boats of 20 to 28 ft. The current installation guide (5611 rev 25) gives a draw of 245 A, where the 2015 copy said 225. The guide asks for a minimum battery of 200 cold cranking amps DIN (380 SAE) and an ANL 150 fuse. The guide gives 1 AWG cable to 7 m of total run and 1/0 to 21 m.
The page rates the brushed motor for two to three minutes' running at 20 C. The control panel switches itself off after about six minutes unused. Sleipner's FAQ wants the tunnel at least three quarters of its diameter below the surface, never less than half. The warranty is two years for leisure use and one for commercial. It transfers to the next owner.
Where each point above comes from
- Sleipner sells it for either end, so it can go at the bow or the stern.The maker's listing
- Sleipner also prints a second, lower thrust figure for when the battery sags under load: 66 lb at 10.5 V.The maker's published rating
- 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
Not sure this is the one? The thruster finder asks about your boat and prices every unit that fits.