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Shaft Drive

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

The system commonly includes a gearbox, coupling, shaft, bearings, stern tube, shaft seal or stuffing box, and an external propeller supported by a strut or stern bearing where required. Alignment carries engine torque while allowing the hull and mounts to move within designed limits.

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.

Alternative Meanings:
  • Shaft Drive

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

    The gearbox, coupling, shaft, bearings, stern tube, seal and propeller form the principal driveline. Depending on the installation, thrust is transmitted through the gearbox and its mounts or through a separate thrust bearing.

    Shaft drive is mechanically direct and widely used, but alignment, shaft angle, underwater appendages and sealing affect efficiency and maintenance. It differs from saildrives and stern drives, whose geared legs transmit power through the hull or transom.