Boat Thruster Guide

What to buy, what it costs, what it takes to fit

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Thruster specs

Lewmar 140TT Gen 2 Package: specs, price and the boats it fits

The 140TT 2.2 kW package is the bigger 140 mm motor with nearly everything to fit it: a 1 m tube, the control box, a joystick, both control cables and the fuse with its holder. It gives 92 lb of push on 12 V, and Lewmar’s chart puts it on boats of about 31 to 40 ft.

Defender prices the package at $2,754. What you still buy is the battery switch Lewmar insists on, about $35 to $107, and a strong starting battery close to the thruster; with cable and a charger, that battery side runs about $583 to $717 by our sums. See the parts.

Owners of this motor report brush trouble. One changed three 140TT 2.2 kW motors in turn, each time with seized brushes and a corroded brush carrier. Keep the motor space dry and clean out the brush dust each season. Fault mode follows three minutes of pushing one way. Motors and controls carry one year of warranty.

Installers will find the wiring figures and dimensions further down. For the rest of Lewmar’s line, read the Lewmar thruster review.

Where this summary comes from (6 sources, read 13 October 2026)

Key facts

  • DIY level 2 of 5 Wiring prep only
  • Thrust 92 lb 42 kgf, Lewmar's rating
  • Boat length 31 to 40 ft Lewmar's chart, by windage. See below
  • Price $2,754 equipment only, defender.com, 13 October 2026
  • Fitted by a yard $9,292 to $17,268 Our estimate at 45 ft, unit and job
  • Voltage 12 V As sold
  • Mounts Tunnel Fixed mount, end not stated
  • To fit it Haul-out The boat comes out of the water
  • Run limit 3 min In one direction, then fault mode

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 2 of 5: Wiring prep only. The yard fits 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 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 DIY

You: 4 to 16 h Yard: 32 to 70 h Electrician: 2 to 4 h Plus a haul-out.

  1. 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.
  2. 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.
  3. 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?

What Lewmar says Not in the listing Lewmar gives its range on its chart, next to this
What Lewmar’s chart says 31 to 40 ft As the 140TT 2.2, the tunnel with this thrust, in 11 to 16 knots. Each kind of boat is in the table.
What our sizing says 32 to 41 ft Full thrust in 15 knots. The longest boat of each kind is in the table.

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 sailboat gets full thrust to 32 ft, and an express cruiser to 41 ft.

The table below tries the Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel 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.

The Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel against each kind of boat, in a 15 knot wind. Our sizing, from the finder’s own rules, beside Lewmar's chart.
Boat Full thrust at 15 knotsStill 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 27 to 32 ft 33 to 48 ftfull thrust to about 10 knots at 48 ft 36 to 40 ftas the 140TT 2.2, class B
Houseboat None 30 to 36 ftfull thrust to about 10 knots at 36 ft 31 to 35 ftas the 140TT 2.2, class C
Catamaran 31 to 37 ft 38 to 55 ftfull thrust to about 10 knots at 55 ft 31 to 35 ftas the 140TT 2.2, class C
Trawler 27 to 32 ft 33 to 47 ftfull thrust to about 10 knots at 47 ft 31 to 35 ftas the 140TT 2.2, class C
Motor yacht None 35 to 47 ftfull thrust to about 10 knots at 47 ft 35 to 35 ftas the 140TT 2.2, 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 34 to 41 ft 42 to 61 ftfull thrust to about 10 knots at 61 ft 36 to 40 ftas the 140TT 2.2, class B
Center console 38 to 40 ft None 36 to 40 ftas the 140TT 2.2, class A

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.

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 The area of the boat the wind can push on: the hull sides, the cabin, the mast and rigging, or the canopy. A tall, boxy boat has a lot of it, and wind force does not care how slowly you are moving. class and a wind band. Our 15 knots falls in its lightest band, 11 to 16 knots.

The Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel is not on the chart by name. Lewmar rates it at the same 92 lb (42 kgf) as the 140TT 2.2. 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 seven 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 $480 to $2,940 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.

The Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel fitted by a yard, from the shortest to the longest boat it is sized for. Our estimate.
Boat length The unit Yard labor Haul-out Batteries, cable, charger Other parts Total
27 ft $2,754 $5,120 to $5,760about 32 hours $480 to $1,300 $583 to $717 $35 to $107 $8,972 to $10,638
45 ft $2,754 $5,120 to $11,52032 to 64 hours $800 to $2,170 $583 to $717 $35 to $107 $9,292 to $17,268
61 ft $2,754 $5,120 to $12,60032 to 70 hours $1,180 to $2,940 $583 to $717 $35 to $107 $9,672 to $19,118

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 12 V: one 12 V battery, at least 280 CCA (Lewmar’s minimum), $257 for the battery; Lewmar’s cable table gives 3/0 AWG, priced on 4/0 AWG, the nearest size cut to length: $180 to $314 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 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.
This package adds
A 1 m tunnel (589102), the blue control box, the joystick (589268), a 10 m auxiliary cable, a 7 m control cable (589802) and a 200 A ANL fuse with holder (589012), by the dealer’s listing, read 13 October 2026. Those parts are not in the table below or in the estimate’s “other parts” line.
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 is the priced parts below, $35 to $107 at Fisheries Supply’s prices on 30 September 2026. The batteries, cable and charger have a line of their own.

Parts the Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel’s box leaves to you, from the makers’ manuals read 30 September 2026. “What to ask for” is Lewmar’s own part or model where its manual names one, otherwise the dealer’s item.
Part What it is What to ask for Dealer price
Main battery switch The switch that cuts the thruster off from its battery when you leave the boat. Gen 2 ABS 589810 (12 V) or 589830 (24 V), or any manual battery switch $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.
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. Lewmar 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. Lewmar 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. Lewmar 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. Lewmar 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.

The Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel, every published figure the site holds, with where each came from.
Thrust and motor
Thrust 92 lb (42 kgf) As printed: 92 lbs @ 12V DC (3 HP)
Motor2.2 kW
Voltage12 V
Fitting
TypeTunnel, fixed mount
End of the boatNot stated
Tunnel diameter140 mm
What it does to the hullTunnel bore below the waterline
Haul-out to fit itYes
Maker’s boat length31 to 40 ftLewmar's selection chart, by windage; the listing prints none
The tunnel
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)
Price and ordering
Price $2,754 equipment only, a dealer's price, defender.com, 13 October 2026
Part number 590092LEW2.2kW Package w/ Joystick & Tunnel, 12 V DC
Documents
Manual Installation manual (PDF)a dealer's copy (the maker publishes none we could find)
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. Lewmar's Gen 2 installation manual
The site’s reviewLewmar thruster 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.

The Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel’s draw, cable, fuse, battery and run limit, as the maker publishes them.
Voltage Draw Maker’s cable Fuse Battery Run limit
12 V 280 Anominal draw 3/0 AWG, the one size Lewmar gives for this model, for any run up to 39 ft of cable counted out and backGen 2 installation manual, Iss.3 200 AGen 2 installation manual, Iss.3 Crank capacity at least the 280 A draw, Lewmar's ruleLewmar Gen 2 installation manual 3 min in one direction, then fault modeGen 2 installation manual

What to weigh

Each point names the fact it rests on.

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
  • Lewmar prints no single length band for it. Its selection chart gives one by windage: 31 to 40 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

What the manual and listings say

This is the note we keep on the Lewmar 140TT Gen 2 Thruster Package with Joystick and Tunnel, written from the maker’s manual, its product pages and the dealer’s listing.

In the box: This package adds a 1 m tunnel (589102), the blue control box, the joystick (589268), a 10 m auxiliary cable, a 7 m control cable (589802) and a 200 A ANL fuse with holder (589012).

Our note

The 2.2 kW 140TT as a Gen 2 package: a 1 m tunnel, the blue control box, joystick, 10 m auxiliary cable, 7 m control cable and a 200 A ANL fuse with holder. The Gen 2 manual rates it 42 kgf (93 lb), with a composite gearbox, 13 kg and a 200 A fuse.

It gives 280 A at 12 V on at least 70 mm² cable to 12 m of total run, battery to thruster and back. That fuse sits below the stated draw, as on every row of the manual's table. Defender prints 92 lb where the manual prints 93. Lewmar's whole battery rule is that crank capacity should at least equal the thruster current.

Run it in one direction for more than three minutes and the system enters fault mode. A thermal switch stops a hot motor, and the manual says wait 20 minutes. The panel powers itself down after 15 minutes idle. The tunnel goes one diameter below the waterline (three quarters at minimum) and at least two diameters long.

The anode is checked after three or four months on a new install, then yearly. The manual says brush the carbon dust out of the motor, especially on an aluminum boat. Three years' warranty on paper, but one year on electric motors, associated electrical equipment and electronic controls. Service by anyone but an authorized Lewmar representative voids the warranty, and removal and refitting are not covered.

Lewmar publishes no boat length. Fisheries Supply's listing says 32 to 40 ft.

Videos

One of Lewmar’s own videos, from its YouTube channel: what changed in the Gen 2 tunnel units. It is the maker’s pitch. Watch it for what the unit looks like and how it goes in, and take any claim back to the figures above.

Lewmar’s own video, on Lewmar’s YouTube channel. The picture is a still from it.

Other sizes and close alternatives

These are Lewmar’s nearest sizes by thrust, in any of its lines.

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.

Compare them side by side

Every model with a page here is listed, maker by maker, on the thruster index.

Where to go next

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.