Boat › Outboard › Lower unit › Faulty water pump

Outboard water pumps are located on top of the lower unit at the base of the driveshaft. The driveshaft turns a flexible neoprene impeller inside a specially-shaped housing to pump the water. The impeller is locked to turn with the driveshaft using a woodruff key or wedge. As the engine RPM increases, the water-pump pumps more water at a higher pressure. A small portion of the water pumped comes out as a small stream through the telltale at the side of the powerhead to let you know the pump is working.

This video shows a method of testing if the water pump is working.

There is no water coming out of the telltale

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The telltale is the jet of water that comes out from the side of the outboard's powerhead. It is there to tell you whether your water pump is working or not.

Replacing the water pump impeller

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An old, brittle impeller can make the engine overheat, and broken pieces can block water passages inside it. I show how to fit a complete water pump kit, including the impeller, gasket and Woodruff key.