page_title: Marine propulsion
section_title: Reciprocating steam engines
hierarchical_section_title: Marine propulsion / Power sources / Reciprocating steam engines
caption_attribution_description: English: The engine room of the SS Ukkopekka Suomi: S/S Ukkopekan konehuone Français&#160;: La salle des machines du SS Ukkopekka
context_page_description: Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or engine turning a propeller, or less frequently, in pump-jets, an impeller. Marine engineering is the discipline concerned with the engineering design process of marine propulsion systems.
  Manpower, in the form of paddles, and sail were the first forms of marine propulsion. Rowed galleys, some equipped with sail, also played an important early role. The first advanced mechanical means of marine propulsion was the
  marine steam engine, introduced in the early 19th century. During the 20th century it was replaced by two-stroke or four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Marine nuclear reactors, which appeared in the 1950s, produce steam to propel warships and icebreakers; commercial application, attempted late that decade, failed to catch on.
context_section_description: The development of piston-engined steamships was a complex process.  Early steamships were fueled by wood, later ones by coal or fuel oil.  Early ships used stern or side paddle wheels, which gave way to screw propellers.
  The first commercial success accrued to Robert Fulton's North River Steamboat (often called Clermont) in US in 1807, followed in Europe by the 45-foot (14 m) Comet of 1812.  Steam propulsion progressed considerably over the rest of the 19th century.  Notable developments include the steam surface condenser, which eliminated the use of sea water in the ship's boilers.  This, along with improvements in boiler technology, permitted higher steam pressures, and thus the use of higher efficiency multiple expansion (compound) engines.  As the means of transmitting the engine's power, paddle wheels gave way to more efficient screw propellers.
  Multiple expansion steam engines became widespread in the late 19th century.  These engines exhausted steam from a high pressure cylinder to a lower pressure cylinder, giving a large increase in efficiency.
caption: SS Ukkopekka uses a triple expansion steam engine
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