1988 Onan 8KW maintanence

Alaskan Sea-Duction · Jan 5, 2017

So my genny is 29 years old. Last summer while in the San Juans, I had an end cap go bad on the oil cooler. I fixed it, but was not confidant it would last the summer. Well it lasted the summer in salt water. I did discover things are different in salt water. Things corrode faster.

Fast forward to yesterday. I have anti-freeze in the genny pan. Vacuumed it out. Noticed a fast drip from the oil cooler. After commandeering the Admiral's beauty mirror and using the zoom side I discovered a small crack on the bottom. So what to do.

I called my local Cummins dealer, I was very surprised at the prices. i.e exhaust manifold/heat exchanger at NW Cummins was $1235! The part number had also changed.

In my research, I found Jacks Small Engine. The same manifold was $936. So $2100 later I have ordered the two heat exchangers ands associated hoses and gaskets. It will take a few weeks to get the parts, but I saved some $$$.

I rely on my genny as I am an electric boat. So after all this is done and it is all working I will be ready for next summer's cruise up the inside passage.

Franky · Jan 5, 2017

That old would put a new one in then pice by pice..a new 8-10 k gen runs about 7500$$ here in calif. Just a note to you? Then putting $$ in parts when it goes and your some where you can get parts? They what do you do. Or gen was 35 years old and we put new on in, boy did do it just in time.....good luck...

Alaskan Sea-Duction · Jan 5, 2017

Franky said:
That old would put a new one in then pice by pice..a new 8-10 k gen runs about 7500$$ here in calif. Just a note to you? Then putting $$ in parts when it goes and your some where you can get parts? They what do you do. Or gen was 35 years old and we put new on in, boy did do it just in time.....good luck...

True but the old one is still running good. $7500 huh. Plus install, another what $ 5,000?

Franky · Jan 5, 2017

No we put our own in. Took 3 days but well worth it, just saying... call the company we got our from and they said to ask what type of boat? Location in the boat? The new ones are way smaller now also. So if you want can get you good price on one? Really not hard to put in...

Franky · Jan 5, 2017

Or pull old one rebuild it? Cheaper also?

Ski in NC · Jan 5, 2017

Onan 8kW MDKD does not have an oil cooler.... ???

Do you mean the coolant heat exchanger? I think those are made by SenDure, check with them.

Lepke · Jan 6, 2017

While you're waiting for parts, there's a bearing in the generator (opposite end from the engine) that should be changed every 5 years. Even on low hours, the lube sealed in the bearing goes bad.

Crusty Chief · Jan 6, 2017

Waiting for parts, hmmmmm, what to do now.......maybe a Scotch and Cigar!

Alaskan Sea-Duction · Jan 6, 2017

Ski in NC said:
Onan 8kW MDKD does not have an oil cooler.... ???

Do you mean the coolant heat exchanger? I think those are made by SenDure, check with them.

It is the heat exchanger which is round and has end caps on it. The other is actually called exhaust manifold, but also works as a heat exchanger and anti-freeze tank.

Alaskan Sea-Duction · Jan 6, 2017

Crusty Chief said:
Waiting for parts, hmmmmm, what to do now.......maybe a Scotch and Cigar!

You got it buddy!!!! You know me well.......

Ex Sailor · Jan 6, 2017

1988 Onan 8 KW Fuel Solenoid

On the subject of an 88 8 KW Onan,
Now and then ... and after I stop our 1988 8KW Onan, it refuses to start.
I have to manually flip the fuel solenoid then it fires right up. The thing will work fine for several cycles of use and then again it's the same problem.

Is the solenoid going bad ? or is there other issue ?

Thanks in advance ... FB

BruceK · Jan 6, 2017

Ex Sailor said:
Now and then ... and after I stop our 1988 8KW Onan, it refuses to start.
I have to manually flip the fuel solenoid then it fires right up. The thing will work fine for several cycles of use and then again it's the same problem.

Is the solenoid going bad ? or is there other issue ?

Very likely the solenoid. Had exactly the same problem. There are 2 "hold" magnets, the initial one which is failing you, and the after it starts one which keeps the plunger across. Check the connections are good.
You probably need a new one unless you fancy visiting the ER every time you want the genset run.
Available from Cummins/Onan, or get the part number and check on Ebay, you may save a bundle, both my OEM replacement and the spare I carry are made in China, the spare was $60 against the $300 OEM.

Ex Sailor · Jan 6, 2017

BruceK said:
Very likely the solenoid. Had exactly the same problem. There are 2 "hold" magnets, the initial one which is failing you, and the after it starts one which keeps the plunger across. Check the connections are good.
You probably need a new one unless you fancy visiting the ER every time you want the genset run.
Available from Cummins/Onan, or get the part number and check on Ebay, you may save a bundle, both my OEM replacement and the spare I carry are made in China, the spare was $60 against the $300 OEM.

Thanks so much... appreciate the info, will get on it as soon as we launch in the spring ... FB

Alaskan Sea-Duction · Jan 8, 2017

Ex Sailor said:
On the subject of an 88 8 KW Onan,
Now and then ... and after I stop our 1988 8KW Onan, it refuses to start.
I have to manually flip the fuel solenoid then it fires right up. The thing will work fine for several cycles of use and then again it's the same problem.

Is the solenoid going bad ? or is there other issue ?

Thanks in advance ... FB

Hey FB. I had the same exact issue. NW Cummins wanted $310. Jack's small engine was $220. 15 minutes to change.

koliver · Jan 8, 2017

Alaskan Sea-Duction said:
So my genny is 29 years old. Last summer while in the San Juans, I had an end cap go bad on the oil cooler. I fixed it, but was not confidant it would last the summer. Well it lasted the summer in salt water. I did discover things are different in salt water. Things corrode faster.

Fast forward to yesterday. I have anti-freeze in the genny pan. Vacuumed it out. Noticed a fast drip from the oil cooler. After commandeering the Admiral's beauty mirror and using the zoom side I discovered a small crack on the bottom. So what to do.

I called my local Cummins dealer, I was very surprised at the prices. i.e exhaust manifold/heat exchanger at NW Cummins was $1235! The part number had also changed.

In my research, I found Jacks Small Engine. The same manifold was $936. So $2100 later I have ordered the two heat exchangers ands associated hoses and gaskets. It will take a few weeks to get the parts, but I saved some $$$.

I rely on my genny as I am an electric boat. So after all this is done and it is all working I will be ready for next summer's cruise up the inside passage.

You are so lucky that you found the problem before it got worse. I had a 4 kw Onan, at about that age it blew through the end cap and dribbled salt water. Unfortunately, the sound shield was not designed to shed dribbled water, so running the generator resulted in that dribble of salt water being forced into the windings of the generator. You know the rest. I now have a Westerbeke with a sound shield that has no floor.

1988 Onan 8KW maintanence

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