Onan 8.5Kw uses oil and coolant

Parts are no longer available. Even if you did rebuild it, you'd be pissing good money after bad on it on ancillary parts.......Save your money for a new one. How much oil and coolant is it using?

My Onan MDKDL 9 KW was an upgrade for the old 8.5. You can get them rebuilt for around 15G. It is worth it

Phasor makes a pretty good generator for the money that's simple, if you want to go the cheaper route for a new one. I would NEVER rebuild a 20+ year old generator.

Which is what got you here in the first place. If the previous owner spent a little more and bought a new gennie, it would still be running fine. Save your money and buy a new generator and be happy for another 20 years. If you rebuild junk, you will still have junk, and if you rebuild the generator you'll be back here in 3 years complaining that the junk you spent good money on rebuilding is now junk again.

I had a 7.5 Kw that was beginning to dollar me. Bought all kinds of spare parts because they were becoming scarce. Lift pumps and rebuilt kits, raw water rebuild kits etc.etc.
The high pressure pump went South ( but I had a used spare !! ) and after $ 1,800.00 to repair it, it went South again within 6 hrs.

I broke down and bought an 8 KW Phasor. My marina is a dealer.
I think it cost about $ 9,000.00 all tolled.
I did most all the work myself.
This cost includes the "Might As Wells" - new fuel lines, valve, Racor, raw water lines and some hardware along with the marina labor and use of the travel lift.
I was able to re-use the original generator mounting base and attached the new pan to that.
The marina picked the old one out and set the new one in for me while I was there.
I removed the old and installed the new one.
I backed into the travel lift well, the old one was out & new one in the engine area pretty quick

No frills.
The new one came with a wiring harness that I used and put the new switches right in place of the old ones.
I did re-use the old power cables because they looked fantastic. No cracked insulation, bright copper and flexible too.

I did not get the sound shield but I did buy the sound shield base in the event I thought it was too loud.
Turns out the base makes and excellent catch basin if it should leak anything between inspections.

It is much more quiet than the Onan and I run it more than I did the Onan.

The old one had about 3800 hrs of use and it ran whenever I started my Detroits. Always ran it loaded too. Simply could not get parts readily and could NOT find anyone to work on it.

The gear driven raw water pump leaked a real small amount of oil almost immediately and the company sent me a new one with in days.

Overall, I am happy with the decision.

If you have mechanical ability you can rebuild the engine by boring the engine and putting in sleeves, use the same pistons, and have rings made if they're not available. Same with the head and pan gasket. The head can be rebuilt by a diesel head shop. If necessary, racing shops have suppliers that make custom pistons, rings and gaskets. Any shop that rebuilds engines, gas or diesel should be able to sleeve the engine. And they may have suppliers for the other stuff.

Stainless, please don’t open duplicate threads. We get penalized by search engines for this.

Barnacle buster is the LAST thing I would do. If it's losing 1/2 a gallon of coolant and it's not leaking externally, and it's not getting into the oil, it's leaking out of the heat exchanger into the sea water. If that's the case, Barnacle buster will just eat more of the heat exchanger away and the coolant will all leak out. You need a new mechanic, then you need to pull the heat exchanger and pressure test it and if good, clean it. But it sounds to me like you need a new heat exchanger.