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Thruster specs
Lewmar 300TT GEN 2: specs, price and the boats it fits
The 300TT Gen 2 is Lewmar’s largest tunnel thruster: twin counter-rotating propellers in a 300 mm tube for the heaviest yachts Lewmar sizes for. Two motors are listed in the US, a 10.8 kW on 24 V and a 15.0 kW on 48 V, both with the bronze gearbox, giving 550 to 616 lb of push by the Gen 2 manual.
Marinedeal is the only US store we found that lists them, at $7,339 for the 24 V and $10,499 for the 48 V. Its part numbers do not match the manual’s, and its product codes are the Gen 1 numbers, so confirm the build with the dealer before you pay. The manual gives the 24 V unit a 500 A fuse and the 48 V one 400 A. See every part.
A thruster this size needs its own battery bank near the bow, which is the biggest cost after the unit. The Gen 2 rules apply: three minutes one way and the system goes into fault mode. The warranty limits motors and electronic controls to one year.
The full spec sheet for a yard sits lower down, and the Lewmar thruster review covers Lewmar’s whole range.
Where this summary comes from (5 sources, read 15 October 2026)
- Marinedeal, Lewmar 300TT 10.8 kW 24 V Gen 2 listing
- Marinedeal, Lewmar 300TT 15 kW 48 V Gen 2 listing
- 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
Choose a size
The Lewmar 300TT GEN 2 Tunnel Thruster comes in two sizes. Each has its own price, wiring and boats it suits, so pick one and the facts, the fit, the cost and the spec sheet below show that size.
| Size | Push | Voltage | Lewmar’s boat length | Price |
|---|---|---|---|---|
| 300TT 10.8kW 24V | 550 lb (249 kgf) | 24 V | Not published | $7,339 |
| 300TT 15.0kW 48V | 616 lb (279 kgf) | 48 V | Not published | $10,499 |
Key facts
- DIY level 2 of 5 Wiring prep only
- Thrust 550 lb 249 kgf, Lewmar's rating
- Boat length 66 to 80 ft Lewmar's chart, by windage. See below
- Price $7,339 equipment only, marinedeal.com, 14 October 2026
- Fitted by a yard $16,106 to $26,693 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 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: 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 59 ft, and a catamaran to 80 ft.
The table below tries the Lewmar 300TT GEN 2 Tunnel Thruster 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 pontoon has no hull body between the logs to bore a tunnel through, and nobody sells one for these boats. | ||
| Sailboat | 65 to 79 ft | 80 ft onlyfull thrust to just under 15 knots at 80 ft | 71 to 80 ftas the 300TT 10.8, class B |
| Houseboat | 49 to 59 ft | 60 to 80 ftfull thrust to about 11 knots at 80 ft | 66 to 75 ftas the 300TT 10.8, class C |
| Catamaran | 74 to 80 ft | None | 66 to 75 ftas the 300TT 10.8, class C |
| Trawler | 65 to 78 ft | 79 to 80 ftfull thrust to just under 15 knots at 80 ft | 66 to 75 ftas the 300TT 10.8, class C |
| Motor yacht | 65 to 78 ft | 79 to 80 ftfull thrust to just under 15 knots at 80 ft | 66 to 75 ftas the 300TT 10.8, 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 | 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.
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 300TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 550 lb (249 kgf) as the 300TT 10.8. 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 five 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 $970 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 |
|---|---|---|---|---|---|---|
| 49 ft | $7,339 | $5,120 to $12,60032 to 70 hours | $970 to $2,360 | $1,226 to $1,495 | $1,181 to $2,119 | $15,836 to $25,913 |
| 65 ft | $7,339 | $5,120 to $12,60032 to 70 hours | $1,240 to $3,140 | $1,226 to $1,495 | $1,181 to $2,119 | $16,106 to $26,693 |
| 80 ft | $7,339 | $5,120 to $12,60032 to 70 hours | $1,490 to $3,860 | $1,226 to $1,495 | $1,181 to $2,119 | $16,356 to $27,413 |
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: two 12 V batteries in series, at least 650 CCA each (Lewmar’s minimum), $720 for both; Lewmar’s cable table gives Over 2 x 4/0 AWG, and that is more copper than the heaviest cable the dealer sells, so this part is a floor, 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.
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.
Key facts
- DIY level 2 of 5 Wiring prep only
- Thrust 616 lb 279 kgf, Lewmar's rating
- Boat length 76 to 80 ft Lewmar's chart, by windage. See below
- Price $10,499 equipment only, marinedeal.com, 14 October 2026
- Fitted by a yard $19,720 to $30,307 Our estimate at 65 ft, unit and job
- Voltage 48 V As sold
- Mounts Tunnel Fixed mount, bow or stern
- 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: 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 62 ft, and a sailboat to 80 ft.
The table below tries the Lewmar 300TT GEN 2 Tunnel Thruster 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 pontoon has no hull body between the logs to bore a tunnel through, and nobody sells one for these boats. | ||
| Sailboat | 69 to 80 ft | None | Off the chart |
| Houseboat | 52 to 62 ft | 63 to 80 ftfull thrust to about 12 knots at 80 ft | 76 to 80 ftas the 300TT 15.0, class C |
| Catamaran | 79 to 80 ft | None | 76 to 80 ftas the 300TT 15.0, class C |
| Trawler | 69 to 80 ft | None | 76 to 80 ftas the 300TT 15.0, class C |
| Motor yacht | 69 to 80 ft | None | 76 to 80 ftas the 300TT 15.0, 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 | 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.
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 300TT GEN 2 Tunnel Thruster is not on the chart by name. Lewmar rates it at the same 616 lb (279 kgf) as the 300TT 15.0. 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 five 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 $1,020 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 |
|---|---|---|---|---|---|---|
| 52 ft | $10,499 | $5,120 to $12,60032 to 70 hours | $1,020 to $2,510 | $1,680 to $1,949 | $1,181 to $2,119 | $19,500 to $29,677 |
| 65 ft | $10,499 | $5,120 to $12,60032 to 70 hours | $1,240 to $3,140 | $1,680 to $1,949 | $1,181 to $2,119 | $19,720 to $30,307 |
| 80 ft | $10,499 | $5,120 to $12,60032 to 70 hours | $1,490 to $3,860 | $1,680 to $1,949 | $1,181 to $2,119 | $19,970 to $31,027 |
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 48 V: four 12 V batteries in series, at least 420 CCA each (Lewmar’s minimum), $1,027 for all four; 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; two GEN5X2 chargers, $293.
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.
- 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, $1,181 to $2,119 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. | Lewmar names none | $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. | 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 | 550 lb (249 kgf) As printed: "590034 TT 300 10.8 24v 300 10.8 14.5 24v Bronze Twin CR 5 Blade 250 550 65 143 500A 589011" - Lewmar Gen 2 TT manual 559231 Iss.3, section 6 |
| Motor | 10.8 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 | 66 to 80 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 | $7,339 equipment only, a dealer's price, marinedeal.com, 14 October 2026 |
| Part number | 59003410.8kW 24 V, bronze gearbox, 24 V DC 59003515.0kW 48 V, bronze gearbox, 48 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 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 |
|---|---|---|---|---|---|
| 24 V | 650 Anominal draw | Over 2 x 4/0, past the common sizes, the one size Lewmar gives for this model, for any run up to 82 ft of cable counted out and backGen 2 installation manual, Iss.3 | 400 A or 500 AGen 2 installation manual, Iss.3 | Crank capacity at least the 650 A draw, Lewmar's ruleLewmar Gen 2 installation manual | 3 min in one direction, then fault modeGen 2 installation manual |
- At 24 V: size the cable for your run, or check the battery you have.
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 | 616 lb (279 kgf) As printed: "590035 TT 300 15.0 48v 300 15.0 20.0 48v Bronze Twin CR 5 Blade 280 616 68 150 400A 589010" - Lewmar Gen 2 TT manual 559231 Iss.3, section 6 |
| Motor | 15 kW |
| Voltage | 48 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 | 76 to 80 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 | $10,499 equipment only, a dealer's price, marinedeal.com, 14 October 2026 |
| Part number | 59003410.8kW 24 V, bronze gearbox, 24 V DC 59003515.0kW 48 V, bronze gearbox, 48 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 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 |
|---|---|---|---|---|---|
| 48 V | 420 Anominal draw | 2 x 3/0 AWG per leg, the one size Lewmar gives for this model, for any run up to 59 ft of cable counted out and backGen 2 installation manual, Iss.3 | 400 AGen 2 installation manual, Iss.3 | Crank capacity at least the 420 A draw, Lewmar's ruleLewmar Gen 2 installation manual | 3 min in one direction, then fault modeGen 2 installation manual |
- At 48 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
- Lewmar sells it for either end, so it can go at the bow or the stern.The maker's listing
- It is sold at 24 V and at 48 V.The maker's and dealers' listings
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: 76 to 80 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 300TT GEN 2 Tunnel Thruster, 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.
10.8kW 24 V, bronze gearbox
The 300TT Gen 2 at 10.8 kW and 24 V: twin counter-rotating propellers in a 300 mm tunnel. The Gen 2 manual rates it 250 kgf (550 lb), 65 kg, with a 500 A fuse.
15.0kW 48 V, bronze gearbox
The 300TT Gen 2 at 15.0 kW and 48 V. The Gen 2 manual rates it 280 kgf (616 lb), 68 kg, with a 400 A fuse.
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.
Other sizes and close alternatives
These are Lewmar’s next sizes in the same line, by thrust.
- One size down: Lewmar 250TT GEN 2 Tunnel Thruster, 308 lb, $4,949.
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 285, 628 lb, $9,287.
- Quick BTQ 300, two sizes, 551 to 595 lb, $11,962 to $13,631.
- Sleipner SE250/300TC, 661 lb, $8,820.
Every model with a page here is listed, maker by maker, on the thruster index.