The water pump on your 7.5 Johnson motor boat works by transferring water to the engine to keep the engine at a safe temperature. Every time you travel 100 hours in your Johnson boat, you need to check the condition of the water pump. Replacing the water pump in a relatively easy task which typically takes about two hours. You can order a replacement water pump from your local boat equipment store.
Remove the bolt clamp attached to the negative battery terminal on your Johnson boat, using a socket wrench. Lift the cable away from the terminal.
Remove the screws attached to the lower engine cover using a Phillips screwdriver. Lift the lower engine cover away from the engine.
Disconnect the shift rod from the shift lever by loosening the shift lever mounting bolt with a wrench and snapping them apart.
Remove the mounting bolts that hold the lower unit of the engine in place. Lift the lower unit away from the motor and move to a clear work space.
Use a socket wrench to remove the retaining bolts that hold the water pump housing to the lower unit. Slide the water pump impeller away from the drive shaft.
Place a layer of marine grease around the new water pump impeller. Reattach the water pump impeller to the drive shaft. Use a putty knife to scrape the gasket from the bottom of the water pump housing. Place a thin layer of gasket sealant on the bottom of the gasket, and reattach it to the bottom of the housing.
Reattach the water pump housing to the lower unit, then fix the lower unit back on to the motor. Fix the shift lever back to the shift rod and secure them together by reattaching the mounting bolt. Place the negative cable back on the battery terminal.
