A vessels transmission system is comprised of the sub-systems on a vessel responsible for transmitting the prime movers mechanical energy to the propulsor, and the propulsors impulse to the hull. The transmission system is itself a subsystem of a vessels propulsion.
A number of methods existing for transferring power. The most common form for larger merchant vessels is direct drive, smaller vessels tending to use higher speed prime movers & gearboxes. Electrical ships are becoming increasingly popular for vessels with compatible operational profiles.