The impeller in a Johnson outboard motor is located just underneath the water pump housing near the top of the motor. It's a black plastic piece designed to circulate the water through the pump to keep the engine cool. Outboard impellers are prone to wear and tear as well as damage from debris being sucked through the water pump.
Remove the screws that secure the top of the Johnson outboard engine cover and unfasten the six screws at the top of the water pump housing cover with a screwdriver.
Lift the pump cup off the top of the water pump shaft just underneath the water pump housing cover and locate the plastic impeller.
Take the impeller off the pump shaft by hand and set it out of the way. Remove any debris from inside the water pump area.
Slide the new impeller onto the water pump shaft and place the pump cup over the top of the impeller.
Attach the water pump housing cover to the top of the water pump with its screws, then secure the engine cover to the top of the motor.
- Never attempt to replace an outboard impeller while the engine is running.