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Discontinued thruster
Lewmar 300TT 10.8 Gen 1 (discontinued): specs, manual and parts
The Lewmar 300TT 10.8 Gen 1 is a tunnel thruster. The motor sits inside the boat and turns a propeller in a tube through the hull. Lewmar has replaced it with its Gen 2 range. Lewmar’s own 2018 thruster controls brochure, which we read on 11 October 2026, calls the units with the black control box the previous generation and the blue box system the next generation. Some dealers still list Gen 1 part numbers.
This page stays up for the owners still running one. It holds the published figures, the part numbers and the manual. You will not find the unit in the thruster finder, the tool here that matches a unit to your boat, or on the compare page. If you need a new thruster, start with either of those.
The published figures
| Type | Tunnel, fixed mount |
|---|---|
| Thrust | 550 lb (249 kgf) |
| As the maker printed it | 250 kgf / 550 lbs (Lewmar manual 500100, electric specification table) |
| Voltage | 24 V |
| Motor | 10.8 kW |
| Tunnel diameter | 300 mm |
| Maker’s boat length | Not published |
| Part number | 59300124V, bronze gearbox59300324V, aluminum gearbox |
| Last price we read | No price held |
| Manual | Lewmar’s manual for it |
Service parts
These are Lewmar’s own part numbers for the parts an owner replaces, where we could find them: the pin that drives the propeller, the propeller, the anode, the brushes, the switch gear, the fuse and the motor. We read them on 11 October 2026. The last column says how we know each one fits this model. Give the dealer your thruster’s serial number from its label when you order.
| Part | Part number | Lewmar’s name for it | How we know it fits |
|---|---|---|---|
| Propellers, right and left hand | 589750, 589751 | Right Hand Propeller, Left Hand Propeller | Lewmar’s manual for this model |
| Propeller washer | 555038 | Plastic Washer | Lewmar’s manual for this model |
| Anode kit | 589550 | Anode Kit | Lewmar’s manual for this model |
| Solenoid (the motor switch) | B8429 | Solenoid | Lewmar’s manual for this model |
| Parallel switch box | 589031 | Heavy Duty Parallel Switch Box 12/24 V (300TT 10.8 kW only) | Lewmar’s manual for this model |
| Coupling | 585014 | Coupling | Lewmar’s manual for this modelThe 300TT parts list shows a coupling and no drive pin. |
| Tunnel gasket | 557035 | Tunnel Gasket | Lewmar’s manual for this model |
| Replacement motor | 587026 | Motor Assembly | Lewmar’s manual for this model |
What the manual and listings say
Lewmar's first-generation 300TT 10.8 tunnel thruster, the one wired through a black control box. It is rated 250 kgf (550 lb) on a 10.8 kW motor in a 300 mm tunnel. Lewmar's 2018 thruster controls brochure calls these the previous generation, replaced by its next-generation blue box system, the Gen 2 range sold today in the same motor sizes.
Lewmar sells a converter so a black box unit can take the newer controls.
Replacement and close alternatives
Lewmar names no replacement for it. The nearest current models are below.
These are Lewmar’s nearest current sizes in the same line, by thrust.
- Nearest below: Lewmar 250TT GEN 2 Tunnel Thruster, 308 lb, $4,949.
- Nearest above: Lewmar 300TT GEN 2 Tunnel Thruster, 550 to 616 lb, $7,339 to $10,499.
Other makers’ current units of the same style, for the same end, within a quarter of its published thrust:
- Sleipner SE210/250TC, 550 lb, $8,325.
- Max Power CT225 (composite leg), 551 lb, $3,991.
- Quick BTQ 250, 265 to 529 lb, $8,624 to $10,571.