The Sleipner SE line is Side-Power's on/off DC tunnel thruster, running from the SE20 (20-25 kg, 110 mm tunnel) to the SE300 (300-340 kg, 48V). It suits most owners who want simple, proven bow or stern thrust. The catch is the 2-3 minute duty cycle and heavy current draw, so cabling and battery placement decide how well it works.
What we like
- Wide range from 110 mm to 300 mm tunnels
- Conservative ratings: the model number is thrust at the lower nominal voltage
- Galvanic isolation and IPC solenoid protection built in
- Ignition-protected versions for gas boats and wet stern installs
- Huge installed base, so parts and techs are easy to find
Watch out for
- 2-3 minute duty cycle before thermal cutout
- On/off control is all or nothing and louder in use
- Big current draw needs heavy cable and a solid battery
- Several larger IP models now point to eVision replacements
If you have looked under the V-berth of a production boat built in the last few decades, there is a fair chance you have already met a Side-Power SE. Sleipner says its tunnel thrusters have gone into more than 350,000 boats, and the SE is the plain on/off version of that family: push the button, it pushes the bow. No speed control, no clever modes, just a DC motor, a gearleg and a propeller in a tube.
That simplicity is the whole appeal. It is also the whole limitation.
Who the SE suits
The SE makes sense for owners who dock a few times a weekend, want help with crosswinds and tight slips, and do not need the boat held against a pier for minutes at a time. It is the default pick for a first thruster on a sailboat or a mid-size cruiser, and the usual like-for-like replacement when an older Side-Power unit finally gives up.
If you are planning a joystick system, or you dock single-handed in strong wind and want the boat pinned to the dock while you step off, look at the SEP PRO and eVision proportional models instead. On/off thrusters do not do that well.
The lineup and how to read the numbers
Sleipner currently lists the SE from the SE20 up to the SE300. The model number is the thrust in kilograms at the motor's nominal voltage, which Sleipner sets at 10.5V for a 12V system and 21V for a 24V system. At full battery voltage you get more. The SE80, for example, is rated 80 kg at 10.5V and 96 kg at 12V. Other brands sometimes quote only the higher number, so keep that in mind when you compare spec sheets.
| Model | Thrust (nominal / full voltage) | Tunnel ID | Sleipner boat guidance |
|---|---|---|---|
| SE20 | 20 / 25 kg | 110 mm | Up to about 23 ft, bow only |
| SE25 | 25 / 30 kg | 110 mm | Up to about 24 ft, bow only |
| SE30 | 30 / 40 kg | 125 mm | 20-28 ft |
| SE40 | 40 / 48 kg | 125 mm | 26-34 ft |
| SE50 | 50 / 62 kg | 140 mm | 27-37 ft, bow only |
| SE60 | 60 / 73 kg | 185 mm | 30-39 ft |
| SE80 | 80 / 96 kg | 185 mm | 33-49 ft |
| SE100 | 100 / 116 kg | 185 mm | 39-56 ft |
| SE120 | 120 / 139 kg | 215 mm | 43-59 ft |
| SE130 | 130 / 160 kg | 250 mm | 43-62 ft |
| SE150 | 150 / 182 kg | 215 mm | 46-66 ft |
| SE170 | 170 / 210 kg | 250 mm | 49-72 ft |
| SE210 | 210 / 250 kg | 250 mm | 56-79 ft |
| SE250 | 250 / 300 kg | 300 mm | 59-82 ft |
| SE300 | 300 / 340 kg | 300 mm | 72-100 ft, 48V |
Boat length is only a starting point. Windage, displacement and how far the tunnel sits from the pivot point matter more than LOA. A flybridge cruiser with a lot of canvas needs a size up from a low sailboat of the same length. Run your numbers through the sizing calculator and then sanity-check the tunnel diameter you can actually fit.
The mid-range models (SE60 through SE100) use twin propellers to get more thrust out of a 185 mm tunnel. Sleipner says the SE80 shares mechanical parts with the SE100, which is why it is one of their most common fits on 35-45 footers.
What matters at install time
Tunnel and position
Get the tunnel as far forward and as deep as the hull allows. Sleipner publishes minimum and recommended tunnel lengths for each model. For the SE80 that is 179 mm minimum and 216 mm recommended, with a minimum water depth over the tunnel equal to the tunnel diameter. The motor can sit at any angle on the tunnel and can be rotated 90 degrees on its bracket, which helps a lot in a cramped forepeak.
Power cabling
This is where most weak installs come from. An SE80 on 12V pulls about 530 A, and Sleipner calls for an ANL 400 fuse and a battery with at least 550 CCA (DIN). An SE100 at 12V pulls about 740 A. At those currents, a long run of undersized cable will drop enough voltage that you lose a real chunk of thrust. Put a dedicated battery near the thruster if you can, keep cable runs short, and size the cable for the actual round-trip length. Our AGM thruster battery and lithium thruster battery pages cover the battery side.
Controls and protection
SE models carry Sleipner's patented Intelligent Power Control (IPC), which adds a short delay between direction changes and stops the thruster if a solenoid sticks. The underwater parts are galvanically isolated from the boat's electrical system, the gearleg is sealed and pre-filled, and a flexible coupling takes up small shaft misalignments. Signal cables are plug-and-play and color-coded to match the wiring diagrams, which makes for fewer mistakes at the panel.
Stern installs
For a stern thruster, Sleipner sells fiberglass stern tunnels that bolt to the transom, plus extra cowls for shallow-draft boats or ones with obstructions aft. The motor ends up in a lazarette that often gets wet, which is where the ignition-protected (IP) versions earn their keep. See our stern thruster installation page for what that job involves.
The weak spots
Duty cycle. Sleipner rates the SE for 2-3 minutes of running at 20°C ambient. On/off models shut down automatically when they get too hot. That is a good safety feature, but if you lean on the thruster to hold the bow into a 20-knot crosswind while someone fumbles a line, it can quit at exactly the wrong moment.
All or nothing. Full thrust or no thrust means short taps and more noise. It works, but it is less refined than proportional control.
Current. Bigger SE models on 12V draw serious amps. If your boat is 24V, use it. If it is 12V and you want an SE100 or bigger, plan the battery and cabling before you buy the thruster.
Product changes at the top end. On Sleipner's own site, the ignition-protected SE120, SE130 and SE170 pages now point buyers to eVision replacements. The standard SE models are still listed, but if you are speccing a large ignition-protected install, check what is current with your dealer first.
How it compares
The closest rival is the Vetus BOW series, which also covers small to large tunnels on 12V, 24V and 48V. Vetus leans on composite props and six-blade designs; Sleipner leans on IPC, galvanic isolation and an enormous parts network. The Sleipner vs Vetus comparison goes through the details. Lewmar, Max Power CT and Quick BTQ are the other usual suspects at this size, and all of them are fine thrusters when installed with proper cable and battery support.
Not sure a tunnel is the right answer at all? Read tunnel vs retractable vs external first.
Verdict
The SE is the sensible default: proven, widely supported, sized conservatively, and available in a size for almost any boat up to about 100 feet. Buy it for occasional docking help. If you want to hold position, run a joystick or keep things quiet, spend the extra on a PRO or eVision model. Either way, the thrust you actually get depends more on the cable and battery than on the box, so talk to us about the install before you pick the model.
Questions people ask
Why does Sleipner list two thrust numbers for one SE model?
Sleipner rates each thruster at its nominal voltage (10.5V on a 12V model, 21V on a 24V model) and again at full battery voltage. The SE80, for example, is 80 kg at 10.5V and 96 kg at 12V. The model number is the lower figure, which is the more honest one to size with.
How long can an SE thruster run?
Sleipner lists a 2-3 minute duty cycle at 20°C ambient. If the motor gets too hot, the on/off models shut down automatically to protect themselves. In normal docking you use it in short bursts, so this rarely matters, but a long hold in wind can trip it.
Can every SE model go in the stern?
No. Sleipner lists the SE20, SE25 and SE50 as bow-only. Most of the rest can be mounted in a bow tunnel or in a Sleipner stern tunnel on the transom.
Do I need an ignition-protected SE?
If the thruster sits in a space where gasoline vapor can collect, yes. Sleipner's IP versions put the electrical parts in a sealed composite housing, which also helps in stern installs that are hard to keep dry.
- Sleipner SE80 12V product page
- Sleipner SE20 product page
- Sleipner SE30 product page
- Sleipner SE100 12V product page
- Sleipner SE300 48V product page
- Sleipner tunnel thruster listing
- Fisheries Supply SE80 listing
Manufacturers update their lines. Confirm current model numbers with us or the maker before you buy.