How do you replace an impeller?

Replacing or checking an impeller is not complicated, but it is important to pay attention to the details. The steps are largely the same for inboard and outboard engines.

Here are the steps to replace an impeller:

Step 1: Close the outboard valve (inboard) or remove the tailpiece (outboard).

Step 2: Remove the pump housing cover (the round sealing plate) by unscrewing it. Some water may come out.

Step 3: Carefully remove the gasket between the cover and the pump housing without tearing it. If the gasket is dry, wet it a little.

Step 4: Look at the impeller and remember the direction of rotation for later.

Step 5: Remove the impeller with an impeller puller.

Step 6: Check that no pieces of rubber remain in the pump housing.

Step 7: Lubricate or spray the impeller and gasket with acid-free petroleum jelly.

Step 8: Replace the impeller in the correct direction of rotation, making sure the vanes drag properly along the walls.

Step 9: Carefully replace the gasket and then replace the sealing plate.

Step 10: Open the outboard valve again (inboard) or replace the tailpiece (outboard). Start the engine and check for cooling water coming out to confirm that the impeller is properly positioned.

Note: Do not remove the impeller from the pump housing with two screwdrivers, as this may damage the pump housing. This is a waste because replacing a pump housing is considerably more expensive than purchasing an impeller puller.