Bow Thruster Guide

Why do I need a Thruster?

A Thruster makes boat handling, especially in tight harbours, much eaiser by gently moving the Bow with a small independently driven prop without having to use the main engine.

What size Thruster do I need for my boat?

It depends on your expectations.

I am buying a new boat but haven�t decided to have a Thruster installed can it be fitted later?

Yes, there are plenty of installers around. It may cost a little extra and will involve hauling the boat and a few days of installation.

What Battery power do I need?

Thrusters have very powerful electric motors and it is recommended where possible to have a dedicated Battery close to the Thruster with a separate charger. This saves the problems of installing expensive, large cables from the main battery bank.

Can I install the Thruster myself?

The majority of the work involves choosing the location and installing the tunnel. A suitably qualified person should always carry out this work.

Can a Lewmar Thruster replace my existing installation/ I have a tunnel and standard fit by another manufacturer?

Yes in most cases providing the tunnel has the same internal diameter.

Today most yachts or motorboats over 45 feet have a bow thruster fitted as standard. The thruster will usually meet the expectations of most customers when using the boat under normal weather conditions. The sizes used by boat builders will vary depending on the boat's intended usage and price level. In today's production boat's of around 45-50, the typical thruster will push the boats bow against a direct side wind of 20-22 knots.
For boat owners who use their boats in more demanding conditions or have a strong current in their local marina, Lewmar can offer upgrades to a higher performance thruster. However, few pleasure craft need a thruster that can push the bow against a direct side wind of more than 25 knots.
The boat's wind area, the lateral wind draft area and the thruster's tunnel position in the hull determine the thruster's performance on a boat. By knowing these factors we can calculate the wind pressure on the boat and the centre point of this wind pressure. However the wind pressure is seldom from right angles and many boat superstructures are quite streamlined so we can reduce the factor slightly. From these calculations we can determine what thrust is needed to counter the wind pressure with the given thruster position.