- 1). Disconnect the spark plug wires. If the engine has electric starting, disconnect the battery cables as well. Place the engine in reverse. Loosen the bolts connecting the upper and lower shift linkage rods and disconnect them.
- 2). Support the lower unit and remove the bolts connecting it to the engine (there are four bolts on the 2-cylinder engine, five on the 3-cylinder model.) Pull the lower unit straight down and out. Secure it in an upright position to work on the water pump. Clean the drive shaft with emery cloth and lightly coat it with grease to ease the removal of the water pump components.
- 3). Remove the four screws holding down the water pump body. Carefully pry up the pump body, using two screwdrivers to evenly free it on both sides. Lift the pump body off of the drive shaft. Pry up the water pump impeller and remove it. Remove the metal drive key from its slot in the drive shaft. Remove the water pump wear plate and clean off any old gasket material or corrosion with emery cloth.
- 4). Slide the new wear plate down over the drive shaft and align it with the screw holes. Lightly grease the drive key and replace it in the drive shaft slot. Slide the new impeller down over the drive shaft, aligning it on the drive key. The Yamaha water pump uses a rubber O-ring around the edge of the water pump body; lightly grease the O-ring and push it into place in the groove. Slide the water pump body down the drive shaft and over the impeller. While pressing down lightly, turn the drive shaft clockwise until the pump body fits into place. Reinstall the four screws on the pump body. Push the water tube grommet into the pump housing.
- 5). Carefully lift the lower unit back into the engine, aligning the drive shaft with its housing. Reinstall the bolts to secure the lower unit in place. Reconnect the shift linkage to complete the job. Be sure to run the engine and confirm that a stream of water is exiting the tell-tale to verify that the water pump is working correctly.
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