Install an Impeller in an Outboard Motor

An impeller.
  • 2-4 hours
  • Beginner
  • 10-50
What You'll Need
Replacement impeller
Socket set
What You'll Need
Replacement impeller
Socket set

The impeller is a very important part of the water pump. It supplies the engine with a constant cool stream of running water. Because the impeller is in constant contact with the water, you may find that it needs to be replaced often, at least more often than other parts on your boat. Impellers tend to rust or corrode if left unattended and the water supply will be cut off to your engine. This can cause the motor to run hot and cause breakdowns. It is very simple to replace an impeller.

Step 1 - Locate the Water Pump

You will need to locate the water pump in order to find the impeller. It is usually at the lower end of the motor near where the propeller is attached. You will need to remove the motor's protective casing in order to locate the water pump.

Step 2 - Remove the Bolts

There are four to six bolts that attach the pump to the drive shaft of the motor. Use your wrench to remove these bolts. It's important that you note which hole had which bolt. They may look exactly the same, but over time there are minute differences that allow the pump to be attached correctly.

Step 3 - Remove the Pump

You will need to use a bit of force to get the pump off of the motor. Pull on it until it loosens. There may be a bit of corrosion or water build up around this area. Use the opportunity to use a calcium, lime, and rust remover to clean up the area. A small, soft-bristled brush will also help you to get the stubborn stuff off.

Step 4 - Locate, Remove, and Replace

Now you need to locate the impeller. It is a small little propeller-like device. If you are not sure what you're looking for, compare the parts to the replacement part that you purchased. In many cases, you will be able to just clean up the impeller. It may not need replacing. Use the same cleaner to see if you can get the build up off. In the case of rust or rot, you should replace rather than try to clean it. Replacing the impeller is just as simple as placing the new one on where the old one came off.

Step 5 - Place the Pump and Replace Casing

Get the pump back into its original position on your motor shaft. Just like in removal, it may take a bit of force to get it back on. Once it's on, replace any covers that you took off in order to remove it. Attach the bolts into their original positions and tighten securely with your socket wrench.

Step 6 - Replace

Clean up the rest of the motor. Replace the casing that you removed and replace any motor covers that you took off in order to accommodate your task.

A well-working water pump will help to keep your outboard motor running cool and help to keep it operational for a longer period of time.