Kohler 7.5R generator burns up impellers?

[VicB]

I have a 7.5R Kohler gasoline generator in my 88’, 3807. Last spring on first startup, I smelled rubber. Raw water impeller disintegrated. I’m talking dust. Changed it out and did great all season. Ran it maybe 10 hours for the whole season. Checked it this spring, looked great. Pliable and no cracks. Ran it 2 or 3 times, maybe an hour so far this season. Last run, I saw heavy steam coming out the exhaust after a couple of minutes of start up and smelled burning rubber again. Shut it down and expect I’ll find smoked impeller again. Any thoughts? I winterize with pink antifreeze. I noticed it is alcohol based, but not sure if I’m ready to say that eats on the rubber. Any thoughts or experience will be much appreciated.
Vic

[bud37]

For the engines try to avoid the alcohol based antifreeze, as that may be the cause here....it does not play nice with some things as you have found out....just look for pink that does not have the flammable label and then read the ingredients to make sure it is alcohol free.....

[Viper]

If the inside of your pump housing is in poor shape, you won't draw water quick enough to lubricate the impeller before it fries. It doesn't take long for that to happen.

Because of the height of the genny's pump above the waterline in the 3807, some guys install a check valve in the raw water line at the seacock to try and minimize this problem. This keeps water in the line at all times right up to the pump. It's a double edged sword though as the check valve can fail in the closed position with age. When that happens, you'll probably replace a couple of impellers before you realize the problem is the check valve. So check to see if you have a check valve threaded into the top of the seacock before you replace the impeller again. If you have one, remove the hose, open the seacock and see if you get a good volume of water coming through. If you don't, you've found your problem.

Keep us posted.

[km1125]

The pink stuff is available in both the alcohol-based versions and polyethylene glycol versions. Definitely prefer the polyethylene glycol for engines.

Surprised your generator didn't shut down with a high temperature alarm. Perhaps when you get the impeller issue resolved, you should check that sensor to see if it's working appropriately.

[VicB]

I like the idea of the check valve. I could see how without it, it could lose its prime all the way down to the strainer. I always check for water output of any of the engines when I start them. The generator pump just doesn’t seem as strong. When I noticed the steam I shut it down immediately.