We stock a selection of high-quality, Italian-made bow thrusters from Quick Nautical Equipment, with both single and double propeller options. We also sell stern thruster tunnels and bow thruster tunnels, as well as accessories such as bow thruster control cable extensions, bow thruster propellers, hand-held remote controls, thruster controllers & propeller anode kits. Replacement parts available include reversing contactor units, fuses, fuse holders, gaskets, elastic coupler joints & splitters.
Complete bow thruster kits are also on offer, including a single propeller bow thruster, tunnel, push-button controller, fuse holder & control cable extension.
What are Bow Thrusters?
A bow thruster is a propulsion device that provides lateral thrust to help with manoeuvrability. Bow thrusters push a boat’s bow or stern sideways in either direction through the water. Bow thrusters can come standard on a new vessel or be retrofitted on boats over 45 feet.
How Do Bow Thrusters Work?
The addition of bow thrusters allows a boat to move to the side (port or starboard) without forward or backward thrust from the engine or rudder. Thrusters use suction to draw in water from one side of the boat and push it out the other side to move the boat in the opposite direction. Fitters install thrusters in through-and-through tunnels on either side of the boat or as external or retractable thrusters. The measure of a bow thruster’s power is in kilogram-force (kgf) which is a gravitational metric unit of force.
The three main bow thruster types are tunnel thrusters, external thrusters and retractable thrusters. You can add bow thrusters to an existing boat or buy a new boat with thrusters already installed.
1. Tunnel Thrusters
Tunnel thrusters are the most common type of thrusters. The tunnel is installed through the bow and below the waterline. Made of composite material, the tunnel can protect the propulsion unit and concentrate the propeller’s thrust. When measuring to find the best location for the tunnel, keep in mind that the top of the tunnel should be at least 75% of its diameter below the waterline, but ideally 1.5 times its diameter. The fitter inserts the propulsion unit into the tunnel from inside the boat.
One of the biggest difficulties with tunnel installation is to create a radius at the end of the tunnel to allow it to suck water into the tunnel without it cavitating. If air bubbles hit the propeller blades, the thrusters become noisy and lose up to 25% of their performance. High-performance boats may use deflectors to minimise speed loss from turbulence.
2. External Bow Thrusters
Not all boats have enough hull space for tunnel or retractable thrusters, so external thrusters are required. They are easy to mount because external bow thrusters don’t require holes in the hull. The biggest downfall for external thrusters is the drag they can create which decreases the boat’s performance. The thruster is also at risk of snagging a buoy and being damaged.
3. Retractable Bow Thrusters
As the name suggests, retractable thrusters can be moved back into the hull when not in use, so there is no risk of snags or unnecessary drag. Electric actuators extend and retract the thrusters. Retractable thrusters require more space for installation compared to the other two types.