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Sleipner · tunnel thruster · bow or stern
Sleipner SAC520: specs, price and the boats it fits
It gives 1146 lb (520 kgf) of push. Sleipner sells it for boats of 85 to 140 ft.
- Haul-out to install
- DIY 2 of 5: wiring prep only
- 2-year warranty
Quick stats
- Thrust 1146 lb 520 kgf, Sleipner's rating
- Boat length 85 to 140 ft Sleipner's own range
- Price per lb of thrust $26.44 Unit only. $33 to $43 installed
- Voltage Not stated Ask the maker before wiring
- Battery Not published Ask the maker before wiring
- Run limit Not published Ask the maker before long use
- To install it Haul-out The boat comes out of the water
- Anodes $138.38 A change, at Fisheries Supply
About the Sleipner SAC520
The SAC520 gives 1146 lb of push from the same 386 mm tunnel as the SAC450, for yachts of about 85 to 140 ft. Like every SAC unit it runs on three-phase AC through a speed controller.
Imtra lists the 380 to 440 V build, mounted horizontal, at $30,300 before a separate tariff line. The manual gives a maximum draw of 73 A at 400 V and a generator load of 47 kVA. See the specs.
Read more
This is the C build, rated continuous at 520 kg; Sleipner also makes an I build that holds 450 kg continuously and reaches 520 kg until the motor warms. Warranty: two years.
Installing it yourself? The installer section has every spec, and the Sleipner (Side-Power) review sets this model against the rest of the Sleipner range.
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 (4 sources, read 15 October 2026)
Will the Sleipner SAC520 steer your boat?
80 FT TRAWLER · BOW · 15 KT WIND
Every knot figure here is wind speed, not boat speed or current.
On a 80 ft trawler the Sleipner SAC520 (1146 lb) steers her in a 25 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 is far more than she needs.
The Sleipner SAC520 on a trawler, by length
- 25 ft78 kt
- 30 ft66 kt
- 35 ft56 kt
- 40 ft50 kt
- 45 ft44 kt
- 50 ft39 kt
- 55 ft36 kt
- 60 ft33 kt
- 65 ft30 kt
- 70 ft28 kt
- 75 ft26 kt
- 80 ft25 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 | No length. More thrust than the boat needs. | |
| Houseboat | 77 to 80 ft | None |
| Catamaran | No length. More thrust than the boat needs. | |
| Trawler | No length. More thrust than the boat needs. | |
| Motor yacht | No length. More thrust than the boat needs. | |
| 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 SAC520 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. The maker gives one range for every boat.
The table tries the Sleipner SAC520 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 77 ft, just past Sleipner’s own range (85 to 140 ft).
It is sized for one kind 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 |
|---|---|
| 77 ft | $38,049 to $48,750$33 to $43 a lb of thrust |
| 80 ft | $38,099 to $48,890$33 to $43 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 $1,440 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.
| Boat length | The unit | Yard labor | Haul-out | Batteries, cable, charger | Other parts |
|---|---|---|---|---|---|
| 77 ft | $30,300 | $5,120 to $12,60032 to 70 hours | $1,440 to $3,720 | None | $1,189 to $2,130 |
| 80 ft | $30,300 | $5,120 to $12,60032 to 70 hours | $1,490 to $3,860 | None | $1,189 to $2,130 |
For every length in the table above.
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
Two of Sleipner’s own videos, from its YouTube channel. They play only when you tap. A maker’s video is its pitch, so take any claim back to the figures on this page.
Know before you buy
What sets this model apart, what it costs to keep, and what to weigh.
Price per pound of thrust
$26.44 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.
Anodes
$138.38 a change- Anode (386 mm gear leg) (SM501180A): $138.38 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
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.
Parts for the Sleipner SAC520
See the Sleipner SAC520 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 SAC450 and SAC520 installation guide, document 5998 rev 15, 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 control panel with its own guide, the S-Link cables, the tunnel and the AC power supply. The guide says the AC units run on standard variable frequency drives.
- Charging
- It runs on the boat's AC power, so there is no thruster battery to charge. The S-Link controls run on the boat's DC supply.
The “other parts” line in the estimate above covers these parts as a range, $1,189 to $2,130 at Fisheries Supply’s prices on 30 September 2026 and 26 October 2026, because the exact items depend on your boat. It runs on AC power, so there is no battery, charger or battery cable to buy. The cost page has what every maker says about each part.
Outside the hull replacement parts in the water
Anode (386 mm gear leg)
The metal that wears away in the water so the drive does not. Sleipner calls it “Anode, aluminium”.
Propeller, left hand (386 mm tunnel)
The propeller on the drive. Sleipner calls it “Propeller, Q-Prop™ LH”.
Listed in the retract mechanical section of this model's page.
Propeller, right hand (386 mm tunnel)
The propeller on the drive. Sleipner calls it “Propeller, Q-Prop™ RH”.
Listed in the retract mechanical section of this model's page.
Gear leg, without propellers
The leg under the motor that turns the propeller. Sleipner calls it “Gearleg w/out propeller”.
Listed on the SAC450 and SAC520 product pages.
Inside the boat replacement parts on board
Drive controller
The electronics that run the motor when you press the panel. Sleipner calls it “SAC thruster drive controller”.
Listed on the SAC450 and SAC520 product pages.
Replacement motor
The electric motor that turns the propeller. Sleipner calls it “AC Motor”.
Read on Sleipner's SAC520 product page.
No part matches. Try the number without spaces, or the part’s name.
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
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 | 1146 lb (520 kgf) As printed: Thrust, continuous 520 kg |
| Motor | 35 kW |
| Voltage | Not stated |
| Run limit | Not published |
| Installation | |
| Type | Tunnel, fixed mount |
| End of the boat | Bow or stern |
| Tunnel diameter | 386 mm |
| What it does to the hull | Tunnel bore below the waterline |
| Haul-out to install it | Yes |
| Maker’s boat length | 85 to 140 ft |
| Price and ordering | |
| Price | $30,300 equipment only, a dealer's price, imtra.com, 26 October 2026 |
| Part number | SAC520/386-C-4H380-440 V AC 3-phase |
| 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 SAC520, with where each came from.
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
It runs on three-phase AC from the boat's generator through a speed controller (VFD), not on a battery bank. This build is for 380 to 440 V, mounted horizontal.
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
- 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.