Onan MDKWB 9 kw oil leak

[Denny Gaultney]

This post on the forum is to discuss a sudden oil leak on an Onan generator.

In my ’97 Tiara I have an Onan MDKWB with 1,330 hours. It has run 151 hours since 2012. Recently replaced two raw water hoses and the Johnson raw water pump (all of which were leaking), and performed oil service with filter using on board oil change system. The enclosure sides and top have been removed.

The oil analysis results returned some sodium and slightly excessive aluminum, iron and copper. It has had infrequent use in the last 7 years and that may have caused the high metals. The high sodium could have been contamination by me since there was a lot of saltwater present due to the raw water leaks at the time of the oil change. I plan to resubmit oil samples in 20 hours on this genset.

After these repairs the genset was run with full load. After observing it run for 10 minutes all looked good. Approximately 30 minutes after start up I found a large oil leak. Oil appeared to be coming from under the front of the oil reservoir base on which the engine sits. Enough oil leaked to have it flow off the enclosure onto the floor next to the gen and become a 1.5″ wide ribbon next to the gen flowing aft along the base. Eventually oil appeared on both sides of the genset at the base.

With a mirror and inspection camera I have not found any leaks above the enclosure pan level. I inspected the area below the oil pressure sending unit, oil filter, dipstick and 360 degrees around the lower engine. After cleaning up the spill I ran the genset again trying to pinpoint the first flow of the leak. It did not come from under the drain, or any place above the enclosure pan level. The first flow spread from under the reservoir near the front. It appears the oil is coming from underneath the oil reservoir.

I removed as much oil as possible using a portable extraction pump. I removed the fittings at the oil drain, cleaned and reinstalled the drain. After this, the genset sat untouched for about a month. When I returned to the boat more oil had seeped out along the left side under the reservoir. I figure this was oil the extraction pump did not get. It reinforces the thought that the leak is underneath the reservoir.

Prior to the large oil leak there has been salt water sitting in the enclosure pan that I had never cleaned up. This must be from the beginnings of the raw water leaks. After removing the enclosure I removed a substantial amount of gunk from around the base of the genset (feeling like a bum for ignoring this genset inside its enclosure all these years.)

Question: Has anyone had a large leak develop from the bolts connecting the oil reservoir to the block, or had the thick cast oil reservoir crack, or develop a hole?

Thanks for your consideration.

Topic

[Jim Rosenthal]

hot water alternative

You might think about plumbing a coolant loop through a new hot water heater. This will get you really HOT water any time you are running that main engine, and it stays hot for a day or two after you shut it off. Virtually all marine water heaters (Raritan, Seaward, IsoTemp) are available with the coolant loop provision, and I can tell you from experience with our Hatteras 36 that it works very well indeed. Also, if you run the engine (and, by extension) the coolant loop, when the water heater is not full, it does not seem to hurt it (I did this, forgetting I had not filled the FW system at the beginning of the season) While I would not do this on purpose, it is much safer than turning on the water heater when there is no water in it.

[Tony Athens]

Excellent choice..Phasor hangs right there with Northern Lights as to a simple/high quality set.. You’ll never look back..Plus, an 1800 RPM unit is so much nicer to be around, even without a sound shield.

Tony

[Denny Gaultney]

Yes sir, it is.

I selected the Phasor 8.5 kw, an 1800 rpm unit. I liked the lack of electronics and the price point.

Thank you for your reply.

[Tony Athens]

Quite an expensive remedy………….. Now that I see you have 2 AC’s, I guess what I was thinking ( more alternator on your mains, maybe a larger battery bank, and a larger inverter ) would not work…. Were you able to find a 1800 RPM unit to meets you needs?

Tony

[Denny Gaultney]

To wrap this post up, I wanted to post the remedy.

With a service call we determined the oil base to be porous.

The part is no longer manufactured. I have been unable to locate one.

Replacement genset has been ordered.

[Denny Gaultney]

We are cruisers. We anchor out a good bit on weekends. Planning to make a 4 month trip north on the ICW this year – our first really long trip.

We are not big generator users – when we are out we generally run it a couple hours to have hot water for showers. We occasionally use it to run A/C to cool down the cabin in summers or heat it up in winter before we retire for the night. But away from the dock we never run the genset overnight for air conditioning. And don’t run it all day long for climate control or anything.

We now have an inverter set up that handles the refrigerator and freezer and small electric needs. And we use a gas cooktop when we anchor out. If we run the main engines at least every 3 days, the house battery bank suffices for our needs, with the exception of hot water.

The boat is a 1997 Tiara 4000 Express. The 9 kw genset was sized to run everything- two a/c, hot water, electric cooktop, microwave, coffee maker, hot water heater, battery charger, etc.

I thought about finding a solution for the hot water and mothballing the gen but we want to have a generator for our trip. And we’ll want one in working order for resale of the boat down the road.

Thank you for your input.

[Tony Athens]

Tell me about your boat and really electrical needs.. Maybe I can offer some “food for thought” as to alternatives..

Tony

[Denny Gaultney]

Thank you, Tony. Went to the boat intending to refill the oil and run it to look again at the leak. But instead I added a quart to the unit and waited an hour. Sure enough oil appeared underneath the base. I scoped out the removal and replacement of this oil base. Not likely to be done in the boat because the 14 bolts holding the engine block and oil base together are likely to be seriously corroded. Definitely beyond my physical capability.

This is the 3600 rpm B spec 9 kw. Loud with the cover off. Noisy with the cover on. Motor is strong and never failed to light up and perform. The generator side has also been trouble free. However, with 1330 hours over 22 years it’s not heavily used.

I have not gotten to asking for quotes but I expect this repair, assuming it’s done out of the boat, is $1500 – 2000 labor including removal from boat (it will lift up through the engine hatch and it’s situated in the center of the boat near the hatch). Found part pricing but no part available – it was around $1600. Sure do dislike these kinds of decisions.

[Tony Athens]

This is a the 9Kw Onan that runs at 1800 RPM correct? If so, then the base engine is a small Kubota unit that is 100%………..But because of the sound shield and general access, you are not in good shape as to sorting this out… I’m sure you know that already.

As to your question–If by “reservoir” you mean the oil pan, then yes, I have seen these corrode thru on Westerbeke sets before.. As to solving the issue, I think you already know the answer—–Serious grunt work as you’ll probably have to pull the unit to find the issue.. Onan does not make service easy.

Tony

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