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Aninboard motor is amarine propulsion system forboats. As opposed to anoutboard motor, where anengine is mounted outside thehull of the craft, an inboard motor is an engine enclosed within thehull of the boat, usually connected to a propulsionscrew by adriveshaft.
Marine diesel engines used in international shipping are the largest, most powerful engines ever produced.[1]
The first marine craft to utilize inboard motors were steam engines going back to 1805 and theClermont and theCharlotte Dundas. Harbour tugs, and small steam launches hadinboard steam engines. In the 1880s thenaphtha engine made its appearance and a few boat engines appeared. Such engines had low power and high fuel consumption.[2] The gasoline (petrol) engine pioneerGottlieb Daimler[2] and Maybach built a four-cycle boat engine and tested it in 1887 on the Neckar River. Sintz in America built several commercially available engines from 1893.
Inboard motors may be of several types, suitable for the size of craft they are fitted to. Boats can use one cylinder to v12 engines, depending if they are used for racing ortrolling.
For pleasure craft, such as sailboats and speedboats, diesel,gasoline and electric[3] engines are used. Many inboard motors are derivatives of automobile engines, known asmarine automobile engines. The advent of thestern drive propulsion leg improved design so that auto engines could easily power boats.
For larger craft, including ships, where outboardpropulsion would in any case not be suitable, the propulsion system may include many types, such asdiesel,gas turbine, or even fossil-fuel or nuclear-generated steam. Some early models used coal for steam-driven ships.
The largest engines in the world are marine diesel engines used to powersupertankers andcontainer ships. The Wärtsilä RT-flex96C produces 109,000 horsepower (81,000 kW), weighs 2,300 short tons (2,100 t), stands 44 feet (13 m) tall, is 90 feet (27 m) long, and has a maximum of 109 rpm.[1]
Some inboard motors are freshwater cooled, while others have a rawwater cooling system where water from thelake,river orsea is pumped by the engine to cool it.
However, asseawater is corrosive, and can damage engine blocks and cylinder heads, some seagoing craft have engines which are indirectly cooled viaheat exchanger in akeel cooler. Other engines, notably small single and twin cylinder diesels specifically designed for marine use, use raw seawater for cooling andzinc sacrificialanodes are employed to protect the internal metal castings.