Rebuild kit for plastic body sea water pumps on Alpha drives For 50 years Sierra has been producing parts engineered to meet or exceed the specifications of marine engine manufacturers and has gained the confidence of engine manufacturers and boat builders to a point of supplying them with OEM parts. Boaters and technicians can be assured a Sierra part will fit right the first time and restore function to OEM specifications. Sierra water pump kits include all you will need to rebuild a sea water pump. An impeller, a wear plate and the required O-rings and associated fasteners make the task to rebuilding the water pump straightforward. We recommend having a spare impeller (Sierra part no. 18-3056) onboard to be prepared in the event of a failure caused by debris or system blockage.