Lewmar Bow Thrusters

Handling a boat in a marina when the wind is pushing against the beam is one of the most challenging situations any recreational skipper faces. A correctly installed bow thruster turns a complex maneuver into a manageable operation, letting you move the bow with precise control. Lewmar systems are designed to operate under sustained load, but their effectiveness depends entirely on the correct match between motor power, propeller diameter, and the length of the tunnel installed in the hull.

Installing a thruster is not a trivial task. You must consider not only the required thrust in kilograms, but also the wire gauge needed to carry the required current without voltage drops. Excessive voltage drop during prolonged use can cause overheating of the contacts and premature motor damage. Our pre-sales technical assistance is designed exactly for this purpose: to verify that the chosen system is consistent with the vessel's electrical setup and dimensions, avoiding purchases based purely on appearance.

When selecting a component for your maneuvering system, always check the manufacturer's specifications regarding compatibility with previous models. Minor technical revisions often require specific installation kits or dedicated control units. Our working method focuses on technical verification of components before shipment, ensuring every part is compatible with your existing configuration.

Maintaining the sacrificial anodes fitted to thrusters is something you cannot ignore. The anode protects the thruster body from galvanic corrosion caused by salt water. If you see that an anode has lost more than 50% of its original mass, replace it immediately. Do not wait for corrosion to attack the bronze or aluminum casing of the motor, because restoration costs would be far higher than the price of a simple replacement kit.

What to Check Before Choosing a Maneuvering System

• Assess the boat's displacement and the surface area exposed to wind to determine the minimum required thrust in kilograms.
• Check the inner diameter of the existing tunnel if you are upgrading or replacing the motor.
• Verify the vessel's electrical system voltage (12V or 24V) and the dedicated battery capacity to sustain the motor's startup current.
• Make sure you have enough space to house the motor and control unit in a dry, ventilated area.
• Plan for periodic replacement of sacrificial anodes to prevent permanent damage to submerged parts.

How do I determine the power needed for my boat?

Power is calculated based on the vessel's length and displacement, plus the lateral surface area exposed to wind. Sailboats with high freeboard require more thrust than motorboats with a lower profile.

What happens if battery voltage is insufficient?

Voltage that is too low causes a higher current draw, leading to overheating of the contactor contacts and potential seizure or damage to the electric motor's windings.

Why is tunnel placement so important?

The tunnel should be positioned as far forward as possible, but submerged to a depth that prevents air ingestion, which would cause cavitation and a dramatic loss of thrust.

What spare parts are essential to keep on board?

In addition to sacrificial anodes, it is wise to always have on hand a set of motor brushes and a spare pair of propellers, as these are the parts most susceptible to impact from floating debris or shallow bottoms.