Marine Propulsion System

A marine propulsion system is the machinery that moves a ship or boat through the water, converting some source of power into thrust against the surrounding water. The earliest mechanical systems used rotating paddle wheels driven by a steam engine, but by the mid nineteenth century the screw propeller had proven more efficient and gradually replaced the paddle wheel on most seagoing vessels. As engines grew more powerful, new propulsion machinery followed: the marine steam turbine gave large ships smoother, higher speed running than a reciprocating engine could, and the marine diesel engine later offered better fuel economy and became the standard for most commercial shipping. Maneuvering at low speed and in confined water led to further specialised propulsion devices, including the bow thruster and the azimuth thruster, both of which let a vessel move sideways or turn without forward way, and the waterjet, which draws in water and expels it through a nozzle rather than relying on an external blade, giving shallow-draft and high-speed craft an alternative to a conventional propeller. Each of these systems solves the same underlying problem, turning stored or generated energy into directed thrust, in a different way suited to a different class of vessel.