Professional Approach to Changing Water Pump Impellers

We normally do our own water pump impellers, and have written about the process before on SetSail, but since Craig Hatton was aboard we thought we’d watch how a professional does this. We learned a lot!

impeller pulling tool

Let’s start with an impeller pulling tool. SetSail correspondent George Backhus wrote about these in an article last year. This was a new tool to us and we picked one up, but had not had the chance to use it yet. It is simple and effective. Just run it into the pump housing, turn the knobs to apply pressure to the impeller, and screw it out.


Here is the withdrawn impeller, and a better view of the tool. Note the cracks in the impeller. This one, and its mate in the port engine, are ready to fail. Craig says to replace the impellers once a year regardless of usage. Ours are overdue, having last been replaced 14 months ago.


The next step is to clean off the old gasket material. Craig uses a custom-made scraper. The next best tool is a sharp putty knife.

salt water pump cover plate

The impeller side of the cover plate is showing quite a bit of wear and it is time to replace it. If a spare were not available, the cover could be reversed.


Inside of the pump housing is a ramp or cam which changes the shape of the impeller blades as they sweep by, creating suction. This needs to be felt with your finger to check for sharp edges caused by wear. If the cam becomes sharp it will cut into the impeller. Ours are still OK.

The next step is to lubricate the impeller with a bit of silicone grease or some Joy detergent, and then twist it as it is slid into the pump housing. We normally compress the vanes with a wire tie, but Craig just shoves them right in – a simpler approach.

Then fit the gasket, taking care to place the wider portion of the gasket in alignment with the ramp/cam.


If you don’t have a cool impeller pulling tool, a pair of screwdrivers can be used, as shown above. This is much easier than our old method of pulling with needle nose pliers! Lever the screwdriver shafts against the edge of the pump housing, forcing the blades into the impeller, and then wedge the impeller out.

Posted by Steve Dashew  (May 15, 2007)

One Response to “Professional Approach to Changing Water Pump Impellers”

  1. Dave Wallace Says:

    Steve, I’ve used the same tool with some success but the last time I changed the impeller I tried something new. I sprayed the shaft with Kano Labs AeroKroil, let it sit for five minutes, and the impeller slid right off with a pair of needle nose pliers. Don’t know if the would always work but I was amazed that time and I’ll certainly try it again next itme. By the way, I’ve also used several other products sold by Kano and have been invariably satisfied. I have no relation to Kano, just a very satisfied customer.

    s/v Air Ops
    Amel Maramu
    Puerto Escondido BCS Mx