Mercury 90 HP Water Pump Impeller Replacement

Tools Needed

• 15 mm ratcheting wrench
• 10 mm flathead screwdriver or small pry bar
• Sand mallet or rubber mallet

Safety

• Ensure the engine is cool before starting work.
• Be cautious when using tools to avoid damaging the gear case.

Steps

1. Locate the five 15 mm bolts and two nuts on the lower unit of the 1997 90 horsepower Mercury two-stroke outboard motor.
2. Remove the five 15 mm bolts and two nuts using a 15 mm ratcheting wrench.
3. Lightly tap the lower unit with a sand mallet or rubber mallet to separate it from the motor.
4. If the lower unit is stuck, use a flathead screwdriver or small pry bar to lightly pry it down.
5. Remove the four 10 mm bolts and the grommet from the gear case using a 10 mm flathead screwdriver or small pry bar.
6. Clean the housing to ensure it is free of debris before reassembly.
7. Install the wear plate base gasket, wear plate housing gasket, and the new impeller, ensuring the keyway is aligned.
8. Grease the impeller blades to prevent damage during the first start.
9. Install the impeller into the housing and turn it clockwise to set it in place.
10. Grease the drive shaft and shift shaft to prevent future issues.
11. Reassemble the gear case and secure it with the cleaned bolts.
12. Trim the motor down and start it up to ensure proper functioning.

Tips

• Greasing the impeller blades helps prevent damage during the first start.
• Ensure the gear case is well-greased to prevent future issues.