How to Change the Water Pump on a Johnson

Changing the water pump on the Johnson outboard motor is a matter of replacing the old parts, including the water pump cover, impeller, keyway and gaskets. Change the water pump at least every couple of years, depending on usage. The Johnson outboard motor water pump is very similar in design to many other outboard motors and is manufactured by the same company that produces the Mercury outboard motor.

Things You'll Need

• Socket wrench set
• Putty knife
• Brush
• Clean cloth
• Marine grease

Instructions

1. Locate the four nuts at the top of the Johnson outboard motor gear box that secures the gear box to the engine housing. Unfasten the four nuts with a socket wrench and slide the gear box away from the engine housing.

2. Place the gear box on a flat surface where you can work comfortably with the motor shaft standing straight up. Unfasten the four bolts that hold the water pump cover to the top of the gear box with a socket wrench.

3. Remove the water pump cover from the top of the gear box, lifting it over the motor shaft. Turn the pump cover over and take the plastic impeller out of the cover by hand.

4. Lift the metal plate and keyway off the top of the gear box. Clean the gasket material debris off the top of the gear box where the water pump cover sits, using a putty knife.

5. Remove any remaining gasket material or debris from the gear box and motor shaft with a brush. Use a clean cloth to remove any grease from the motor shaft and top of the gear box.

6. Place the new rubber gasket on the top of the gear box, sliding it down over the top of the motor shaft. Slide the metal plate over the motor shaft and sit it on top of the rubber gasket with the rounded side of the plate facing up.

7. Place a thin layer of marine grease around the inside edges of the new water pump cover. Slide the new impeller upside down into the water pump cover.

8. Place the new metal keyway in the slot at the top of the gear box and fit the round rubber gasket inside the lip of the new water pump cover over the new impeller. Slide the new water pump cover and impeller assembly over the motor shaft and line up the keyway with the notch in the impeller.

9. Fasten the water pump cover to the gear box with bolts. Slide the Johnson outboard motor gear box back onto the motor housing and secure it to the housing with the bolts.

Tips & Warnings

• To avoid burns, never attempt to change the water pump on the Johnson outboard motor while the engine is still hot.

References

• Outboat-Boat.com: How To Replace a Johnson/Mercury Water Pump Impeller 90hp Outboard
• Boat Part Store: Outboard Cooling System
• Stern Drive: Johnson Outboard Motor Water Pump Kit