Maneuvering thruster

Bow thrusters make docking easier, since they allow the captain to turn the vessel to port or starboard side, without using the main propulsion mechanism which requires some forward motion for turning;[1] The effectiveness of a thruster is curtailed by any forward motion due to the Coandă effect.

During vessel design, it is important to determine whether tunnel emergence above the water surface is commonplace in heavy seas.

Externally mounted bow thrusters have one or more propellers driven by a small reversible electric motor which provides thrust in either direction.

The added control provided by a bow thruster helps the captain to avoid accidents while docking.

Some waterjet bow thrusters can be configured to provide forward and aft auxiliary propulsion, or even full 360-degree thrust.

A ship equipped with tunnel thrusters, indicated by the circled "X" markings above the water line
A bow thruster in action. Note the transversal water jet.
A retractable bow thruster lowered under the front of a sailboat