Onan 8KW Gen.

I fired up the Gen. for the first time since launch in June and noticed in the initial water discharge some granular material(s) sort of kitty litter and saw dust looking stuff. The discharge stream seemed irregular ( a bit of flow and a bit of sputtering ) I did not run it long enough to monitor temperature etc. for fear of doing something to this thing.

Does anyone have any idea what this material could have been ( other than bits of impeller ??? ) and if there is potential blockage of the exchanger tubing ... ?


Of note: this is a new boat to us, I have never owned a Gen. before nor have I seen this one running for an extended time.

Thanks in advance ... FB

What did the surveyor have to say about it?

We'd all be purely speculating without first hand inspection. It could be any number of things. Advise getting a tech who knows these.

I would say it could be a critter that nested up there???

Impeller pieces likely would not make it out of the exhaust. They would have to get thru the heat exchanger first.

I would check the impeller though. I would also check the intake side of things....thru hull and strainer and such.

You were wise to shut it down. Certainly debris coming out the exhaust is not normal, and indicates something is in there that shouldn't be there. Perhaps a bird or a mouse built a nest while the boat was hauled of the winter. You may have washed them out. Regardless, check that everything is clear before you start again.

This doesn't sound like the impeller. The impeller is probably black rubbery, and pieces probably wouldn't get past the heat exchanger anyway. But you should check the impeller before first start every spring, and make sure that you find and remove any fins that have broken off.

caltexflanc said:

What did the surveyor have to say about it?

We'd all be purely speculating without first hand inspection. It could be any number of things. Advise getting a tech who knows these.

Click to expand...

LOL ..... the surveyor said there was an Onan 8KW Generator .....

Rossland said:

You were wise to shut it down. Certainly debris coming out the exhaust is not normal, and indicates something is in there that shouldn't be there. Perhaps a bird or a mouse built a nest while the boat was hauled of the winter. You may have washed them out. Regardless, check that everything is clear before you start again.

This doesn't sound like the impeller. The impeller is probably black rubbery, and pieces probably wouldn't get past the heat exchanger anyway. But you should check the impeller before first start every spring, and make sure that you find and remove any fins that have broken off.

Click to expand...

Thank you, Very good point re: wildlife building a nest or something .... I never thought of it. But good advice in having a good check just to be sure.

Baker said:

I would say it could be a critter that nested up there???

Impeller pieces likely would not make it out of the exhaust. They would have to get thru the heat exchanger first.

I would check the impeller though. I would also check the intake side of things....thru hull and strainer and such.

Click to expand...

Thank you, this was granular stuff, sort of beige in colour and small enough to go through the exchanger tubes, I think .....

Ya'll got dirt diver wasps up there? They love to build nests of mud inside of any small openings. I have to clean out vent openings all the time because of these insects!

"dirt wasps" = "mud daubbers"

Ex Sailor said:

LOL ..... the surveyor said there was an Onan 8KW Generator .....

Click to expand...

Typical................

And we pay them money for that!

Maybe some rust from the exhaust elbow? When was the last time it was replaced? If you still had a good water flow I would say your impeller is working.

Sounds like zinc debris. Normal. Mixer is a nice welded ss unit, does not shed debris.

Sounds like prostate trouble to me. Oops, wrong blog.

This whole thread is way overboard. My goodness. Follow the advice here and you'll be tearing down the generator.

You only have one question to answer... did it overheat???

If it did not, run the generator. You yourself said its a new boat to you. That most likely means that it has not been run for awhile.

Could be any number of things, but if it does not overheat then the cooling system is working properly.

ksanders said:

This whole thread is way overboard. My goodness. Follow the advice here and you'll be tearing down the generator.

You only have one question to answer... did it overheat???

If it did not, run the generator. You yourself said its a new boat to you. That most likely means that it has not been run for awhile.

Could be any number of things, but if it does not overheat then the cooling system is working properly.

Click to expand...

While I was going to write something similar, I paused. Because if he does run it and there is an obstruction, it could do more than just overheat...like water backing up into the cylinders. Not likely but I didn't want to say "just run it" and if it doesn't overheat, it is fine. I, personally, would do a bit of "mechanical" diligence before I started again.