Onan Impeller

stevocom · Post by **stevocom** » Thu Sep 16, 2010 2:01 pm

Well fired up the genny and literaly NO water was pumping. Pulled apart the water pump and the removed the impeller which by the way was not all that bad, very little rubber was missing but some. Is there a possibility some of the missing rubber is stuck somewhere and could this be the cause for NO water exiting? What would the best method of back flushing be? Who stocks these impellers?

fpawn1 · Post by **fpawn1** » Thu Sep 16, 2010 2:17 pm

What yr is the generator? Could you move the impeller?

koviak · Post by **koviak** » Thu Sep 16, 2010 5:02 pm

Parts are availible from Cummings in Pa. You can try posting on smokestack.com They have a wealth of info. on gensets. My unit is a 1989 and did not pump when I bought the boat, rebuilt the impeller and replaced all hoses, runs good now.

stevocom · Post by **stevocom** » Thu Sep 16, 2010 11:22 pm

1978, yes the impeller spins freely, do you have to back flush this system? what is the best method?

g36 · Post by **g36** » Fri Sep 17, 2010 10:43 am

when you say the impeller spins freely are speaking of turning the pulley and looking at the impeller itself and see it spinning or that the pulley spins easily in the pump housing?

i was thinking maybe the hub of the impeller is spinning and the actual impeller itself may not be. do you have any kind of airleak that could be between the seacock and the impeller air would be sucked in easier than water would

Danny Bailey · Post by **Danny Bailey** » Fri Sep 17, 2010 1:47 pm

McMaster Carr sells a magnetic drive 110V centrifugal water pump for about a third of what Onan sells a repair kit for. Thats what I had on my Onan before I junked it and installed a Northern Lights.

rossjo · Post by **rossjo** » Fri Sep 17, 2010 8:53 pm

http://SmokStak.com (no "E")

reelfishin · Post by **reelfishin** » Sat Sep 18, 2010 10:48 pm

Sounds like a suction problem to me. Clogged strainer or screen on the boat. If the screen is almost clogged could you have suction on a hose causing it to collapse?

Big D · Post by **Big D** » Sat Sep 18, 2010 11:18 pm

Do you have a strainer, if so, is it above the water line or below?

reelfishin · Post by **reelfishin** » Sun Sep 19, 2010 8:17 am

You should have a intake screen under the boat that keeps seaweed etc out and then you should have a inline strainer on the suction line. Also posted you could have a air leak on the suction side or impeller not spinning by the generator. You could always disconnect the suction line at the generator and put a shop vac on the line to see if you get water to the generator.

stevocom · Post by **stevocom** » Mon Sep 20, 2010 12:26 pm

well the bits and pieces of broken off impeller have to go somewhere correct? do they exit the system of do they get stuck somewhere?

Sea Play'n · Post by **Sea Play'n** » Mon Sep 20, 2010 12:29 pm

stevocom wrote:1978, yes the impeller spins freely, do you have to back flush this system? what is the best method?

Simply connect a garden hose to the raw water intake at the onan water pump and turn it on. Water should flow back through the strainer and overboard through the seacock.

You did check to see if the seacock was open, didn't you?

reelfishin · Post by **reelfishin** » Mon Sep 20, 2010 4:50 pm

You said that there was not much missing on the impeller. If they are really small they might have gone on through the unit and out. If they are bigger they could clogg up something and the generator would run hot. We are trying to determine first if you have water coming to the generator. That needs to be solved first.

aaronbocknek · Post by **aaronbocknek** » Mon Sep 20, 2010 5:09 pm

good afternoon everyone, when i ran into a similar problem last year with my 1976 mcck onan, my mechanic suggested we change the thermostats and flush the system with mary-kate on and off. here is what we did.
after removing the housing for the thermostats---these buggers are only .5 inch round and roughly an inch high--- we rinsed the thermostat housing with on and off--- it's an acid that will eat away any marine crud-- then removed the cylinder drain cock and cleaned the drain out with a small pick. then, ontop of the thermostat housing there is a bypass hole that bypasses the thermostats until the unit comes up to temperature. we used the same small pick to clean out that hole too..... we removed the old thermostats which had never been replaced since the unit was installed judging by the corroded condition and then popped in the new ones. installed the new housing gasket, assembled the housing and hoses then closed off the seacock. holding the water hose, john poured about a cup of on and off into the hose and used the mechanics switch on the control box to briefly suck the solution into the manifold. he let that sit and do its work for about 10 minutes, then ran the unit while pouring the remaining bottle into the hose. shut the unit down and let the entire solution sit for roughly 20 minutes. reattach the intake hose to the strainer/seacock and run the unit. you will be amazed at the crud that comes out the exhaust as the marine critters are dissolved by the acid solution. make sure your intake under the boat is clear by blowing air or water in reverse, and that your water pump is turning when the unit is running. the more this genset is run, the better it will be for it. the initial problem w/ mine was it was never used and everything built up in it. i now run my genset twice a month for 45 minutes at a 50% load after it warms up for 10 minutes. after you take the load off, let it run for 10 more minutes then shut it down. it runs like a dream and never smells hot. the exhaust flow is great and holds steady at about 100 degrees. hope this helps. but again, do not over look the thermostats.

reelfishin · Post by **reelfishin** » Mon Sep 20, 2010 6:22 pm

Now that is a interesting solution. I shall keep that in mind for future use. Thanks for the information.

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Onan Impeller

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