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Thruster specs
Lewmar RT185 MX Gen 2: specs, price and the boats it fits
The RT185 MX Gen 2 is Lewmar’s retractable bow thruster: it lowers out of a housing in the hull when you switch the panel on and tucks away when you switch it off. The piece cut out of the hull usually becomes its closing door, so the bottom stays smooth under way. It gives 214 lb of push at 12 or 24 V, for boats of about 51 to 60 ft on Lewmar’s chart.
Defender prices the 12 V unit at $8,687 and the 24 V one at $9,034, against $3,427 for a 185TT tunnel unit of the same push. The housing and the lowering gear come with it. The 24 V version draws about half the current, which eases the cable; batteries, cable and charging run $866 to $1,135. See every part.
Fitting it means building a watertight compartment and bonding a flange into the hull, a yard job. Never run it out of the water: the manual warns the motor will overspeed. The panel powers it down after five minutes idle. Warranty: three years, with one on the motor and controls.
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)
- Defender listing (the database’s price)
- Lewmar retractable thruster manual 55110070 iss.4 (housing, closing door, five-minute power-down)
- Lewmar Thruster Selection Guide (boat length by windage)
- Lewmar Gen 2 TT installation manual 559231 Iss.3 (three minutes one way, then fault mode; warranty one year on motors and controls)
- Lewmar, About (making boat hardware in Havant, England, since 1946)
- Lippert Components acquires Lewmar Marine Limited, 1 August 2019
Key facts
- DIY level 2 of 5 Wiring prep only
- Thrust 214 lb 97 kgf, Lewmar's rating
- Boat length 51 to 60 ft Lewmar's chart, by windage. See below
- Price $8,687 to $9,034 equipment only, defender.com, 13 October 2026
- Fitted by a yard $17,361 to $29,462 Our estimate at 55 ft, unit and job
- Voltage 12 V or 24 V As sold
- Mounts Retractable Drops down, bow
- 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 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: 40 to 88 h Electrician: 2 to 4 h Plus a haul-out.
- Cut the hull and fit the housing and mechanism Yard 40 to 88 h Nobody publishes an hours figure. Fisheries Supply says installation is significantly more expensive than a tunnel, and that is too loose to turn into a number. So this is the tunnel’s own banded figure plus a quarter, which keeps it above a tunnel as the distributors describe it.
- 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 36 ft, and an express cruiser to 62 ft.
The table below tries the Lewmar RT185 MX Gen 2 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.
| Boat | Full thrust at 15 knots | Still a fit, in lighter wind | Lewmar’s chart |
|---|---|---|---|
| Pontoon & tritoon | Not listed. A retractable drops down inside the hull, and a pontoon has no hull depth to drop into. | ||
| Sailboat | 41 to 49 ft | 50 to 73 ftfull thrust to about 10 knots at 73 ft | 56 to 60 ftas the 185TT 6.0, class B |
| Houseboat | 31 to 36 ft | 37 to 54 ftfull thrust to about 10 knots at 54 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Catamaran | 46 to 56 ft | 57 to 80 ftfull thrust to about 11 knots at 80 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Trawler | 41 to 48 ft | 49 to 73 ftfull thrust to about 10 knots at 73 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Motor yacht | 41 to 48 ft | 49 to 73 ftfull thrust to about 10 knots at 73 ft | 51 to 55 ftas the 185TT 6.0, class C |
| Bass & flats | Not listed. A retractable needs hull depth to drop into, and these planing hulls have almost none forward. | ||
| Wake & ski boats | Not listed. A retractable needs hull depth to drop into, and these planing hulls have almost none forward. | ||
| Express cruiser | 52 to 62 ft | 63 to 65 ftfull thrust to about 14 knots at 65 ft | 56 to 60 ftas the 185TT 6.0, class B |
| 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.
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 RT185 MX Gen 2 is not on the chart by name. Lewmar rates it at the same 214 lb (97 kgf) as the 185TT 6.0. 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 six 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 $550 to $3,860 at these lengths, with 5 to 7 days out of the water, worked from eight yards’ own rate cards. The hours are our own estimate. 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 |
|---|---|---|---|---|---|---|
| 31 ft | $8,687 to $9,034 | $6,400 to $7,200about 40 hours | $550 to $1,500 | $866 to $1,135 | $328 to $803 | $16,831 to $19,672 |
| 55 ft | $8,687 to $9,034 | $6,400 to $15,84040 to 88 hours | $1,080 to $2,650 | $866 to $1,135 | $328 to $803 | $17,361 to $29,462 |
| 80 ft | $8,687 to $9,034 | $6,400 to $15,84040 to 88 hours | $1,490 to $3,860 | $866 to $1,135 | $328 to $803 | $17,771 to $30,672 |
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 700 CCA (Lewmar’s minimum), $360 for the battery; Lewmar’s cable table gives 2 x 3/0 AWG, priced on 2 x 4/0 AWG, the nearest size cut to length: $360 to $629 for the red and black cable and the lugs; a GEN5X2 charger, $146.
- At 24 V: two 12 V batteries in series, at least 370 CCA each (Lewmar’s minimum), $513 for both; Lewmar’s cable table gives 2 x 2/0 AWG: $228 to $403 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. That manual is written for the tunnel units. A retractable unit brings its own housing, so there is no tunnel to buy.
- 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.
- 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".
- 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, $328 to $803 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 |
|---|---|---|---|
| Control panel | The buttons or joystick at the helm. One helm, one panel: a second steering station needs a panel of its own. | 589268 single joystick, 589267 dual joystick, 589222 and 589223 pads | $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. | Gen 2 AUX loom, 2 to 22 m | $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. | Lewmar 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. | 589006 (589010 for the T2 fuse) | $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. | 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.
| Thrust and motor | |
|---|---|
| Thrust | 214 lb (97 kgf) As printed: 214 lbs (97 kgf) |
| Motor | 6 kW |
| Voltage | 12 V or 24 V |
| Fitting | |
| Type | Retractable, drops down |
| End of the boat | Bow |
| Tunnel diameter | 185 mm |
| What it does to the hull | Large hull opening below the waterline |
| Haul-out to fit it | Yes |
| Maker’s boat length | 51 to 60 ftLewmar's selection chart, by windage; the listing prints none |
| Price and ordering | |
| Price | $8,687 to $9,034 equipment only, a dealer's price, defender.com, 13 October 2026 |
| Part number | Not held for this listing |
| 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 review | Lewmar 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.
| Voltage | Draw | Maker’s cable | Fuse | Battery | Run limit |
|---|---|---|---|---|---|
| 12 V | 700 Anominal draw | 2 x 3/0 AWG per leg, the one size Lewmar gives for this model, for any run up to 36 ft of cable counted out and backretractable thruster manual, iss.4 | 500 Aretractable thruster manual, iss.4 | Crank capacity at least the 700 A draw, Lewmar's ruleLewmar retractable thruster manual | 3 min in one direction, then fault moderetractable thruster manual |
| 24 V | 370 Anominal draw | 2 x 2/0 AWG per leg, the one size Lewmar gives for this model, for any run up to 118 ft of cable counted out and backretractable thruster manual, iss.4 | 325 Aretractable thruster manual, iss.4 | Crank capacity at least the 370 A draw, Lewmar's ruleLewmar retractable thruster manual | 3 min in one direction, then fault moderetractable thruster manual |
- At 12 V: size the cable for your run, or check the battery you have.
- 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
- It is sold at 12 V and at 24 V.The maker's and dealers' listings
What to weigh
- The boat comes out of the water to fit it: it needs a large hull opening 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: 51 to 60 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 RT185 MX Gen 2, written from the maker’s manual, its product pages and the dealer’s listing.
In the box: The solenoid, the ICU control box and a 2 m motor loom are in the box. The panel, its loom, the fuse and holder are bought.
12 V
A retractable: the unit lives in a housing let into the hull and drops when used. It is a bigger yard job than a tunnel and a mechanism to keep working. Every Lewmar goes on with the boat out of the water. Defender rates the RT185 MX Gen 2 at the same 214 lb (97 kgf) as the biggest 185TT, at 12 or 24 V.
The 24 V unit is about four percent dearer. The Gen 2 tunnel manual does not cover this unit, but its control rules name one: a retractable powers down after five minutes idle, a tunnel unit after 15. 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 for any unit. This row is the 12 V version; Defender prices it separately, read 12 October.
24 V
This row is the 24 V version; Defender prices it separately, read 12 October.
Videos
One of Lewmar’s own videos, from its YouTube channel: its older swing-down retractable docking a small cruiser, the nearest thing Lewmar has filmed to this model. 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.
Other sizes and close alternatives
These are Lewmar’s nearest sizes by thrust, in any of its lines.
- One size up: Lewmar 250VRTT Vertical Retractable, 353 lb, $29,417.
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.
- Sleipner SRVP80 PRO, 212 lb, $10,510.
- Max Power Compact Retract, three sizes, 154 to 220 lb, $7,370.
- Quick BTR 185, six sizes, 143 to 231 lb, $12,436 to $17,991.
Every model with a page here is listed, maker by maker, on the thruster index.