> The bow thruster is a propulsion device fitted to certain types of ships to improve maneuverability.
> The thrust unit consists of a propeller mounted in an athwartships tunnel and provided with some auxiliary drive such as an electric or hydraulic motor.
> During operation water is forced through the tunnel to push the ship sideways either to port or starboard as required.
> The unit is normally bridge controlled and is most effective when the vessel is stationary
> In a controllable-pitch type thruster, a servo motor located in the gear housing enables the propeller blade pitch to be altered, to provide water flow in either direction. With this arrangement any non-reversing prime mover, like a single-speed electric motor, may be used.
> The prime mover need not be stopped during maneuvering operations since the blades can be placed at zero pitch when no thrust is desired.
> The drive is obtained through a flexible drive shaft, couplings and bevel gears. Special seals prevent any sea water leakage into the unit.
> The complete assembly includes part of the athwartships tunnel through which water is directed to provide then thrust.