sternthrusters

A stern thruster is a propulsion device installed near the stern of a vessel to provide lateral (sideways) thrust at low speeds. It is designed to improve maneuverability during berthing, unberthing, and other precision movements, and it commonly complements the vessel’s propellers and bow thruster. Stern thrusters are especially valuable in confined harbors, during docking, and when dynamic positioning systems are in use.

There are two main configurations. Fixed-direction stern thrusters are mounted on the port or starboard side of the stern and push water from aft toward the side to generate sideways force. Azimuth stern thrusters, by contrast, can rotate their propeller housing to produce thrust in any horizontal direction, offering greater maneuverability without needing rudder-dependent steering at very low speeds. Many installations place a stern thruster in a stern tunnel or through-hull arrangement, and some models are retractable to reduce drag when not in use.

Drive systems for stern thrusters are typically electric or hydraulic. Power ranges vary widely with vessel size—from a few tens of kilowatts on small craft to several hundred kilowatts or more on larger ships. Control is by helm, wheel, joystick, or integrated with a vessel’s autopilot or dynamic positioning system. Redundancy and dedicated power supplies are common to ensure operation in critical phases of maneuvering.

Applications include merchant ships, ferries, offshore-support vessels, workboats, and yachts. The use of stern thrusters improves precision and safety in constrained environments, reduces reliance on tug services, and enhances overall maneuverability, though they add energy demand and maintenance considerations. See also bow thruster and dynamic positioning.