A motorboat has one engine or more that propel the vessel over the top of the water. Boat engines vary in shape, size and type. Engines are installed either inboard or outboard. Inboard engines are part of the boat construction, while outboard engines are secured to the transom and hangs off the back of the boat. Motorboat engines run on gasoline or diesel and fuel. Engines come in various types. Engines vary in fuel type such as: gasoline, diesel, gas turbine, rotary combustion or steam. Motorboats are commonly used for recreation, sport or racing.