Runabout (boat) - Propulsion

Propulsion

Runabouts can be powered by inboard engines, outboards, jet drives, or inboard-outboard (I/O) drives. Engines can be gasoline or diesel systems.

Inboards have the engine block permanently mounted within the hull of the boat, with a drive shaft and a propeller to drive the craft underneath the hull, and a separate rudder to steer the craft. To give the engine block the proper angle a plinth is typically used.

Outboards are packaged drive units, containing the engine block, linkage gears, and the propeller within a single unit. Outboard drives are mounted to the transom and are mechanically turned to the left or right to steer the craft, either directly with a tiller, or through a remote steering system leading to a steering wheel mounted on the boat's console. Outboard drive units are typically designed to act as both propulsion and rudder.

Jet Drives are drive units have a propeller enclosed in a pump-jet that draws water from underneath of the hull and expels it through a swiveling nozzle in the stern. They are highly maneuverable and tolerant of shallow water, but need larger engines and use more fuel than the other alternatives.

Inboard-Outboard drives are a hybrid, with an engine block mounted within the hull, but linked to a lower drive unit mounted to the transom containing the propeller which is pivoted for steering the craft, similar to an outboard motor. An outdrive also serves as a rudder.