Impeller

An impeller is a rotating wheel with curved vanes that pushes fluid outward or along a channel. In a liquid-cooled motorcycle engine, the water pump impeller circulates coolant between the engine and radiator.

On jet skis and other personal watercraft, an impeller in the jet pump draws water in under the hull and forces it out through the steering nozzle, providing thrust. Impeller pitch affects acceleration and top speed.

Water pump impellers can corrode or wear their seals, causing leaks from the weep hole and overheating. Jet ski impellers get chipped by sand, stones and debris, which reduces performance and causes cavitation, so inspect them regularly and avoid shallow, sandy water.