Motor Ship

a ship propelled by an internal-combustion engine; the most common type of self-propelled vessel. The power of the main engine in a motor ship is transmitted to a propelling device directly or through reduction gearing; mechanical or hydraulic couplings may also be used. Diesel-electric ships—ships with diesel main engines and electric power transmission to electric propeller motors—were formerly included in this category.

The first motor ships were built in Russia: the tankers Wandal (1903) and Sarmat (1904) and the paddle-wheel tugboat Mysl’ (1907), all designed for operation on the Volga, and the tanker Delo (1908), designed for operation on the Caspian Sea. The Wandal was equipped with screw propellers, three 88-kilowatt (120-hp) engines, and electric transmission to the propeller shafts; the Sarmat had a mechanical drive to the propeller shaft. The Delo was equipped with two main engines with a total power of 735 kilowatts (1,000 hp). The first twin-engine submarine—the Russian Minoga (1908)—was equipped with two 88-kilowatt four-stroke reversible internal-combustion engines. In other countries, cargo motor ships appeared in 1911 with the launching in Denmark of the tanker Selandia, equipped with two 920-kilowatt (1,250-hp) engines. In 1913, 70 of the world’s 80 motor ships were of Russian registry.

The marine internal-combustion engine was developed through increases in efficiency, reductions in weight and dimensions, improvements in reliability, and increases in power, leading to the replacement of steam-powered ships. In 1930, according to Lloyd’s Register of Shipping, motor ships accounted for approximately 10 percent of the merchant marine; by mid-1974, according to the same source, this fraction had risen to 88.5 percent of ships with a displacement of 100 register tons or more, and the tonnage of motor ships accounted for 63 percent of the gross tonnage of the world’s self-propelled fleet. Motor ships accounted for approximately 83 percent of the ships ordered and under construction at the end of 1974 with a deadweight of 2,000 tons or more, equaling approximately 43 percent of the total deadweight and approximately 63 percent of the total horsepower of all main engines being installed.

Two-stroke and four-stroke, slow-, medium-, and high-speed internal-combustion engines are used as main engines in motor ships. By 1975, power ratings for marine engines had reached 36,300 kilowatts (48,000 hp, in Japanese motor ferries), and in-stalled-power ratings had reached 2 × 29,400 kilowatts (2 × 40,000 hp, in Japanese container ships). For high power ratings the main engines of motor ships can compete with gas- and steam-turbine installations.

The auxiliary marine machinery on motor ships includes air compressors and compressed-air tanks for starting the engines, a system for cooling the pistons and cylinders with seawater and fresh water, and fuel and oil filtering and high-pressure supply equipment. The heat of exhaust gases from medium- and highpower engines is used to produce steam in waste-heat boilers; the steam is used for the generation of electricity and other ship’s needs.