Nitrile impeller. 15-32" (12mm)D with a shaft diameter of 5-16" (8mm) and an overall diameter of 1 1-4" (32mm). Single flat drive. 8 Blade Jabsco impellers fit a variety of pumps in marine applications, including marine engine water pumps and bilge pumps. It is common practice to inspect and replace flexible impellers annually as preventative maintenance against pump failure. Spare water pump impellers for the engine coolant system should be kept on board. Neoprene construction is suitable for engine cooling pumps and nitrile for bilge pumps or transfer duties where water is heavily contaminated with oil or diesel.