The replacement brass Jabsco 11831 water pump faceplate locates on the front of the pump providing access to the impeller and a smooth surface for the rubber impeller to rotate correctly.
Water pumps are lazy so they would much rather pump air than water - because it is easier to do so!
So, to ensure the engine is continually water-cooled by the pump it is important to service the pump regularly. The water pump faceplate, or water pump end cap, is integral to the efficiency of the pump. In order for the vacuum in the pump to build, so water can be pumped, the faceplate must be in good working order, and should generally have a flat surface on the inside face for the impeller to rotate on.
If the faceplate wears it can allow air to be sucked into the pump, allowing the pump to pump air instead of water. Wear on the inside surface of the water pump faceplate generally looks like circular cuts or grooves, particularly where the impeller blades have been rotating. If there is signs of wear, simply adding a new gasket to the faceplate usually has limited, if any, success so a new faceplate may be the way forward.
Boat engine water pump faceplates can wear over time as the rubber impellers spin rapidly in the pump housing between the faceplate and the wearplate, the constant rotation can cause wear.
Wear on the faceplate usually looks like circular cuts or grooves having been cut into the faceplate by the impeller rotation. The faceplates should generally have a flat face on the inside surface, so the impeller can rotate freely. Significant wear can reduce the efficiency of the pump, and can even prevent the pump from pumping water so should be replaced on a major service.