Editing Diesel engine (section)

===Watercraft===
[[File:8 cylinder Burmeister & Wain Diesel engine for MS Glenapp 1920.png|thumb|One of the eight-cylinder 3200 I.H.P. Harland and Wolff – Burmeister & Wain diesel engines installed in the motorship ''Glenapp''. This was the highest powered diesel engine yet (1920) installed in a ship. Note man standing lower right for size comparison.]]
[[File:InleHandCrank.webm|thumb|right|Hand-cranking a boat diesel motor in [[Inle Lake]] ([[Myanmar]])]]
The requirements for marine diesel engines vary, depending on the application. For military use and medium-size boats, medium-speed four-stroke diesel engines are most suitable. These engines usually have up to 24 cylinders and come with power outputs in the one-digit Megawatt region.<ref name="Reif_2014_12" /> Small boats may use lorry diesel engines. Large ships use extremely efficient, low-speed two-stroke diesel engines. They can reach efficiencies of up to 55%. Unlike most regular diesel engines, two-stroke watercraft engines use highly viscous [[fuel oil]].<ref name="Reif_2014_13" /> Submarines are usually diesel–electric.<ref name="vB_2017_1289" />

The first diesel engines for ships were made by A. B. Diesels Motorer Stockholm in 1903. These engines were three-cylinder units of 120&nbsp;PS (88&nbsp;kW) and four-cylinder units of 180&nbsp;PS (132&nbsp;kW) and used for Russian ships. In World War I, especially submarine diesel engine development advanced quickly. By the end of the War, double acting piston two-stroke engines with up to 12,200&nbsp;PS (9&nbsp;MW) had been made for marine use.<ref name="Mau_1984_9_11" />