a self-propelled vessel in which the electric drive for the propellers receives its power from an onboard electric power plant, from storage batteries, or from an external electric system. A distinction is made between turboelec-tric vessels, whose prime movers are turbines, and diesel-electric vessels, whose prime movers are dieseis.
The principal advantage offered by an electric watercraft lies in the ability of an electric motor to alter the speed of rotation of the propeller shaft smoothly and to reverse the direction of rotation quickly. Such an ability improves maneuverability. Wear is reduced if a high-speed internal-combustion engine operating at a constant speed serves as the main power plant.
The use of electric motors and generators makes it possible to install the vessel’s power plants in the most efficient locations and in locations independent of the propelling motors; the need for bulky reduction gears is thereby eliminated. Electric watercraft, however, have never been widely used, because of the large amount of electric power lost in transmission (10–15 percent), the cost and relative complexity of the power system as a whole, and the greater labor outlays required for repair and operation as compared with those for vessels with other power systems.
Comprising approximately 1.8 percent of the total number of vessels in the world’s merchant fleet with a registered tonnage of more than 100 tons, electric watercraft are used primarily as icebreakers, tugboats, and ferryboats. The development of shipboard nuclear power plants is opening up new possibilities for the development of electric watercraft.