Generator Impeller

[Gervie]

On our boat we have an Onan MDKAV 9KW generator. During a recent cruise the generator decided to eat its impeller. I looked up the part number in the Onan parts list and found it to be 132-0375.

I called around the area and found a couple. The replacement part number for this impeller is Sherwood 10077K.

The old one came out pretty easy as some of the vanes were missing. The new one was a bit difficult. I used Dawn dish washing soap to make the impeller more pliable. Then tried to stuff it into the non-round opening. No luck. Then I cut a length of string and tied a loop on one end. Then I threaded the bitter end through the loop making a lasso. I put it around the impeller about mid-way and tightened it up so the vanes would collapse. The impeller slide right in and after replacing the o-ring that came with the new impeller and putting on the cover plate it was ready to go. It fired right up and I was back in business.

I am going to get some cable ties to replace the string for next time. They lock and are easier to handle.

Last item is to buy a spare impeller. I had spares for the engines but not the generator. That problem is solved.

I hope this helps someone who might be reluctant to DIY.

 

[Four Suns]

I have the same impeller/water pump on my Onan even though it is a little bigger. I've had to change mine underway as the kids will go nuts if they don't have TV, etc.

The heat exchanger is easy to open up and get the pieces out of the old impeller. On mine it's a single bolt on the end that comes out, the end plate comes off and all the impeller pieces should be there.

 

[Gervie]

Gary, that is the next thing I will do now that I am back in home port. Thanks for the info on the heat exchanger. Could the pieces gone on through the closed raw water system?

The impeller had just 47 hours. Would you think it went bad from not using the generator enough?

We found out the impeller went bad when we had to wait for a slip and they parked us for the night in the launch ramp well. Since I didn't have a spare, I had to string a couple of power cords over the well next to me to get power. Lesson learned, carry a spare.

 

[Skip]

Gervie,
I had to do the same impeller drill on my boat, and we have the same gen set. I used silicone spray to get the new impeller in, while gently rotating it. Worked fine. Recommend you hang on to the old impeller. I used a shop vac on the inboard side of the heat exchanger to suck out all the rubber chunks of the old impeller. You need to get them out as they will impede water flow and cooling efficiency of the heat exchanger. Once you think you have all of them out, lay all the pieces of the old impeller on a clean white rag, compare this to the new impeller, and assess how much of the old impeller you have successfully extracted from the heat exchanger. This is the method Frank W recommended to me (less the shop vac part) and 200 hours later generator and new impeller are running fine. I will put a new impeller in the gen set concurrent with new main impellers next spring. This to me is cheap annual maintenance insurance. The nice thing is that the Onan shuts itself off and gives you a cooling water flow error code when the impeller heads south.

regards
Skip

 

[Four Suns]

The raw water cooling on Onan generators is extremely simple so I don't think you have to worry about anything getting past the heat exchanger. If it did, it went out the exhaust. These diesels are low-tech and low-rpm run-forever engines. The cooling system is not like the mains where you have all kinds of coolers and aftercoolers daisy chained on each other. Whenever I've opened up the heat exchanger end plate, all the pieces were there.

 

[Tenacious]

I've got the same gen. Impeller was eaten up this past weekend I have new one but want to be Sure to recover broken fingers. Where exactly did you access the heat exchanger from? Do you have any photos by chance? Thanks.

 

[Sum Escape]

On our boat we have an Onan MDKAV 9KW generator. During a recent cruise the generator decided to eat its impeller. I looked up the part number in the Onan parts list and found it to be 132-0375.

I called around the area and found a couple. The replacement part number for this impeller is Sherwood 10077K.

The old one came out pretty easy as some of the vanes were missing. The new one was a bit difficult. I used Dawn dish washing soap to make the impeller more pliable. Then tried to stuff it into the non-round opening. No luck. Then I cut a length of string and tied a loop on one end. Then I threaded the bitter end through the loop making a lasso. I put it around the impeller about mid-way and tightened it up so the vanes would collapse. The impeller slide right in and after replacing the o-ring that came with the new impeller and putting on the cover plate it was ready to go. It fired right up and I was back in business.

I am going to get some cable ties to replace the string for next time. They lock and are easier to handle.

Last item is to buy a spare impeller. I had spares for the engines but not the generator. That problem is solved.

I hope this helps someone who might be reluctant to DIY.

Gervie,
The shop vac method recomended by Skip works great, just be sure to prop open the exhaust flapper so a good vacuum is established. All the pieces of the impeller will be in the vac without having to take apart the heat exchanger!
Also, annually change the impeller. Easy and cheap. And be sure to check the inside of the pump for any scoring...some fine sandpaper will smooth out any burrs or scrapes from sand ingestion and help the impeller to last a bit longer.
Carry that spare!