Onan MCCK impeller change

[BarryK]

Hi all,

I have a 1990 MCCK J series genset. I successfully removed the 4 screws from the impeller cover but the cover is frozen and I can't get it off. I sprayed it with penetrating oil and I will have another go at it tomorrow. I've had the boat for about 18 months now. I have no idea when it was changed last. I'm thinking about a rubber strap wrench.

Any help would be appreciated.

Thanks,
Barry

[bud37]

Someone may have used silicone when they put it back on.........try a razor blade around the edge. Fishing line will cut into as well if silicone was used.

[BarryK]

Thanks Bud!

I tapped gently with a hammer and an improvised metal tool (gear puller) to distribute the force. I was able to scrape off the corrosion with a pick and then get a scalpel blade in between the cover and body of the pump (oriented flat with respect to the cover). Then I got a flexible putty knife in between and it came off easily.

tools for impeller.jpg

I loosened the screws mounting the pump to the frame. I left them in place to avoid dropping them into the bilge. This allowed me to angle the pump up enough to access the lower screw. I had to remove the carburetor and free up the fuel pipe. This only takes a few minutes. The 4 cover screws came off pretty easily. The lower one is a bit challenging but possible with care.

generator.jpg

I got most of the old gasket material off with a plastic scraper and careful use of a razor. I finished up wet sanding with 1000 grit sandpaper flat on a granite countertop, working the impeller cover over top of the sandpaper.

impeller cover.jpg

It's pumping water nicely now!

[Viper]

Check the exhaust nipple in the middle of the exhaust manifold, the arrow is pointing to it. There was a recall on the original ones due to a few deaths from CO poisoning. They would rust from the inside out and get pinholes in them. The approved replacement nipples were stainless steel. If that's not what you have, you should consider replacing it.