We may earn a referral commission from some links on this page. It doesn't change your price or our recommendations.
Thruster specs
Sleipner SE250/300TC: specs, price and the boats it fits
The SE250 is the largest on/off tunnel thruster Defender lists from Sleipner. It delivers 661 lb of push through a 300 mm tube from twin counter-rotating propellers, for yachts of about 60 to 84 ft, on 24 V.
It sells for $8,820. The very wide tube, a control panel, a main switch and fuses add about $1,189 to $2,130. It needs its own 24 V bank near the bow, and with the heavy cable and charging we put that at $1,700 to $1,787. Fitting a 300 mm tube is a major yard job, so price the whole installation before you commit. See the parts list.
Sleipner also builds a variable-speed PRO version of this size, which it says runs close to continuously at half power. The SE250 is push-button, rated for 2 to 3 minutes at a time. Two years of warranty, transferable.
Installers will find the wiring figures and dimensions further down. For the rest of Sleipner’s line, read the Sleipner (Side-Power) review.
Where this summary comes from (3 sources, read 12 October 2026)
Key facts
- DIY level 2 of 5 Wiring prep only
- Thrust 661 lb 300 kgf, Sleipner's rating
- Boat length 60 to 84 ft Sleipner's own range
- Price $8,820 equipment only, defender.com, 28 August 2026
- Fitted by a yard $18,069 to $28,477 Our estimate at 65 ft, unit and job
- Voltage 24 V As sold
- Mounts Tunnel Fixed mount, bow or stern
- To fit it Haul-out The boat comes out of the water
- Run limit 2 to 3 min Duty cycle at 20 C ambient
Every figure here is the maker’s or a dealer’s, except the fitted cost, which is our estimate. The full spec sheet is further down.
How much of the install is yours
DIY levels
- Level 5: Owner install. No yard, no electrician.
- Level 4: You fit 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 fits 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 h Yard: 32 to 70 h Electrician: 2 to 4 h Plus a haul-out.
- Cut, bond and fair the tunnel; fit the gear leg, motor and propeller Yard 32 to 70 h 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 h 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 h Our estimate. Nobody publishes a time for the final connections and test on their own.
Your part needs:Heavy battery cableCrimping big lugs
A qualified marine electrician should make the final connections and test them before first use. Hours are labor only.
Is it right for your boat?
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 64 ft, and a sailboat to 80 ft. The maker gives one range for every boat.
The table below tries the Sleipner SE250/300TC 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 down to 54 ft, just past Sleipner’s own range (60 to 84 ft).
| 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 | 72 to 80 ft | None |
| Houseboat | 54 to 64 ft | 65 to 80 ftfull thrust to about 12 knots at 80 ft |
| Catamaran | No length. More thrust than the boat needs. | |
| Trawler | 71 to 80 ft | None |
| Motor yacht | 71 to 80 ft | None |
| 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. | |
Reading the two length columns. 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 falls short of what the boat needs by no more than 10 percent, and gives the whole figure only in the lighter wind named. On a boat shorter than the first column’s shortest length, the unit is more than the boat needs.
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 fitting. The compare page sets this unit beside others.
What it costs fitted
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 $1,060 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. Your own yard will have its own opinion. The cost page builds the same figures line by line.
| Boat length | The unit | Yard labor | Haul-out | Batteries, cable, charger | Other parts | Total |
|---|---|---|---|---|---|---|
| 54 ft | $8,820 | $5,120 to $12,60032 to 70 hours | $1,060 to $2,610 | $1,700 to $1,787 | $1,189 to $2,130 | $17,889 to $27,947 |
| 65 ft | $8,820 | $5,120 to $12,60032 to 70 hours | $1,240 to $3,140 | $1,700 to $1,787 | $1,189 to $2,130 | $18,069 to $28,477 |
| 80 ft | $8,820 | $5,120 to $12,60032 to 70 hours | $1,490 to $3,860 | $1,700 to $1,787 | $1,189 to $2,130 | $18,319 to $29,197 |
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 12 October 2026.
- At 24 V: four 12 V batteries, two strings of two in series, at least 665 CCA each (Sleipner’s minimum), $1,440 for all four; Sleipner’s cable table gives 2/0 AWG: $114 to $201 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.
What else you buy
What follows comes from Sleipner’s SE80 to SE150 installation guide, document 2687 rev 30, 2025, read 30 September 2026.
- In the box
- The gasket, bolts and anode come with the unit. The SEP guides call the power controller "the included PPC unit".
- 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.
- 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.
The manual’s words, 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 is the priced parts below, $1,189 to $2,130 at Fisheries Supply’s prices on 30 September 2026. The batteries, cable and charger have a line of their own.
| Part | What it is | What to ask for | Dealer price |
|---|---|---|---|
| Tunnel tube | The fiberglass, aluminum or steel pipe the thruster sits in, bonded through the bow. | SM13010, SM13015 (39 in, 59 in) | $852–$1,315300 mm fiberglass tunnel tubes up to 60 in (1.5 m) long (Sleipner Side-Power), at Fisheries Supply, read 16 October 2026. |
| Control panel | The buttons or joystick at the helm. One helm, one panel: a second steering station needs a panel of its own. | SM8960G single joystick, SM8950G touch panel | $219–$374Side-Power touch panel and single joystick, VETUS push-button panel, Lewmar single joystick, at Fisheries Supply. |
| Control cable, panel to motor | The thin cable from the helm to the motor. Sold by length. | Side-Power 4-wire control cable, by length | $29–$173Side-Power control cables, VETUS panel cables, Lewmar Gen 2 connecting cables, at Fisheries Supply. |
| Main fuse | A slow-blow fuse of the ANL type at the battery, in the size the maker prints for the model. | Side-Power ANL fuse, the rating in the yard table below | $18–$57Side-Power ANL fuses, Blue Sea ANL fuses, at Fisheries Supply, read 16 October 2026. |
| Fuse holder | The block the ANL fuse bolts into, with a cover. | SMANLHOLD (SMANLHOLD-C with a cover) | $27–$93Egis and Blue Sea ANL fuse blocks, Side-Power ANL fuse holders, at Fisheries Supply, read 16 October 2026. |
| Main battery switch | The switch that cuts the thruster off from its battery when you leave the boat. | Side-Power manual main switch, 350 or 600 A, or the automatic AMS | $35–$107Egis m-Series 300 A, Blue Sea e-Series 350 A and HD-Series 600 A on/off switches, at Fisheries Supply, read 16 October 2026. |
| Control-circuit fuse and switch | A small fuse, and often a switch, on the thin wire that powers the panel or control box. | Sleipner names none | $8–$12Blue Sea in-line ATO fuse holders, at Fisheries Supply, read 16 October 2026. |
| Battery cable and lugs | The two heavy cables from the battery to the motor, sized to the length of the run. The wiring calculator sizes them. | Sleipner names none | In the electrical line |
| Battery bank | A cranking-type bank near the motor, sized by the maker's cold cranking amps. The battery calculator checks it. | Sleipner names none | In the electrical line |
| Charger or charge feed | How the thruster bank gets charged: a shore charger of its own, a DC-to-DC charger or charging relay from the boat's system, or a charger built into the unit. | Sleipner names none | $146–$305NOCO GEN5X2 shore charger, Victron Orion-Tr Smart DC-DC charger, Blue Sea ML-ACR charging relay, at Fisheries Supply. |
| Glass, resin, filler and sealant | What bonds the tube or housing into the hull and seals the gear leg. | Sleipner names none | Not priced |
The cost page has the whole list with what every maker says about each part.
For the yard and the installer
The full spec sheet, grouped the way a yard reads it. Every figure is the maker’s or a dealer’s, with its source.
| Thrust and motor | |
|---|---|
| Thrust | 661 lb (300 kgf) As printed: up to 300 kg of thrust at 24V; 250 kg at 21V |
| Thrust under load | 551 lb at 21 V |
| Motor | 11.4 kW |
| Voltage | 24 V |
| Fitting | |
| 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 fit it | Yes |
| Maker’s boat length | 60 to 84 ft |
| The tunnel | |
| 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) |
| Price and ordering | |
| Price | $8,820 equipment only, a dealer's price, defender.com, 28 August 2026 |
| Part number | 99967124 V |
| Documents | |
| Manual | Installation manualon the maker's product page |
| 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. Sleipner's warranty statement, effective 1 April 2022 |
| The site’s review | Sleipner (Side-Power) review |
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 |
|---|---|---|---|---|---|
| 24 V | 670 Anominal draw | 2/0 AWG for up to 22 ft of cable counted out and back. Longer runs take heavier cableinstallation guide | ANL 500installation guide | 700 CCA DIN minimumSleipner installation guide, SE250, document 5244 rev 20 (2025) | 2 to 3 min duty cycle at 20 C ambientproduct page, "Motor cycle duty" |
- At 24 V: size the cable for your run, or check the battery you have.
What holds up and what to weigh
Each point names the fact it rests on.
What holds up
- 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: 551 lb at 21 V.The maker's published rating
What to weigh
- The boat comes out of the water to fit it: it needs a tunnel bore below the waterline.The mounting: a bore through the hull, or a housing recessed into it
What the manual and listings say
This is the note we keep on the Sleipner SE250/300TC, written from the maker’s manual, its product pages and the dealer’s listing.
In the box: Gasket, bolts and anode with the unit. The panel, its cable, the fuse and main switch are bought.
Our note
The biggest brushed tunnel unit Defender lists. It has twin counter-rotating props in a 300 mm tunnel, 24 V only, for boats of 60 to 84 ft. It is rated 300 kg at 24 V and 250 at 21. The dealer's page does not print the tunnel size. The 300 in the model name is Sleipner's convention.
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.
Videos
Two of Sleipner’s own videos, from its YouTube channel: how the tunnel mouth changes the thrust you get, and the current E-series tunnel units. They are the maker’s pitch. Watch them for what the unit looks like and how it goes in, and take any claim back to the figures above.
Other sizes and close alternatives
Sleipner also sells this thrust built another way. Each has its own page:
- Proportional, brushless (eVision): Sleipner E300/300TC, $12,825.
These are Sleipner’s next sizes in the same line, by thrust.
- One size down: Sleipner SE210/250TC, 550 lb, $8,325.
- One size up: Sleipner SE300/300TC, 750 lb, $12,850.
These are other makers’ units of the same style, for the same end, within a quarter of its published thrust. Each is that maker’s nearest match.
- VETUS Bow Pro Boosted 300, 661 lb, $11,291.
- Lewmar 300TT GEN 2 Tunnel Thruster, two sizes, 550 to 616 lb, $7,339 to $10,499.
- Max Power CT325 (24 V), 717 lb, $6,510.
Every model with a page here is listed, maker by maker, on the thruster index.