Shaft Drive

A propulsion arrangement in which an inboard engine turns a propeller through a shaft passing through the hull.

The principal driveline includes a gearbox, coupling, shaft, bearings, stern tube, shaft seal or stuffing box, and propeller. An external strut or stern bearing supports the shaft where required. Depending on the installation, thrust is transmitted through the gearbox and its mounts or through a separate thrust bearing.

Alignment must transmit engine torque while allowing the hull and mounts to move within designed limits. Shaft angle, underwater appendages and sealing affect efficiency and maintenance. This arrangement differs from saildrives and stern drives, whose geared legs transmit power through the hull or transom.

Misalignment, worn bearings, damaged seals, corrosion and vibration can cause leakage or failure. Coupling fasteners, engine mounts, shaft runout, anodes, rope-cutter clearances and emergency means of controlling water entry require inspection appropriate to the installation.

Terms with the same meaning:
Shaftdrive