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Old 30-05-2016, 10:58   #1
jwa
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Oil in raw water exhaust - trans oil cooler failed?

Hi
This weekend, we had an apparent failure of our transmission oil cooler. We have a Pearson 424 with Westerbeke W58, and fortunately, we have a spare trans oil cooler.
There is one item that I am a bit confused about. While motoring at full throttle, we suddenly noticed smoke and thick black oil coming from the exhaust along with the normal water. We shut down immediately, noticing as we did that the temp gauge had climbed from normal 190 to over 200, along with oil pressure dropped to almost nil.
Question is, is it possible that the oil pressure gauge has shared inputs from engine and trans? Not understanding why we would have low engine oil pressure if the trans oil cooler failed? It makes sense that the temp would rise with hot trans oil gunking up the raw water circuit I guess. Last week, I had changed out the raw water impeller, along with topping the coolant and checking all areas for abnormal temps with an infrared temp sensor. Heat exchanger was flushed and acid-cleansed in April. Engine was running perfectly at about 180 to 190 since then.

Canít see how the above symptoms would result from anything but a blown oil cooler, right? Just guessing on a shared oil pressure gauge causing the low reading?

Thanks!
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Old 30-05-2016, 11:11   #2
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Re: Oil in raw water exhaust - trans oil cooler failed?

I would say "motoring along at full throttle" on what a 25 y/o would be the first sign of impending disaster.
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Old 30-05-2016, 11:20   #3
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Re: Oil in raw water exhaust - trans oil cooler failed?

I'm confused. You don't recommend motoring at full throttle on a 25 year old boat?
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Old 31-05-2016, 09:59   #4
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Re: Oil in raw water exhaust - trans oil cooler failed?

I am NOT a trained mechanic but have the usual cruiser knowledge yada yada. You should not have black smoke from any part of your tranny as far as I can imagine. You might get oil. Check the tranny oil level. The oil gauge should be for the motor and not the tranny. Big ship/big boat engines might have a tranny pressure gauge but they would be rare for your engine.

I don't know your engine but assume it is fresh water/coolant cooled which is then cooled by raw water. The engine oil should be cooled by the coolant so should not be exiting the exhaust water via a cooler leak.

Most cruiser engines should not be run at full throttle except for short periods from what I know. It puts too much stress on the poor motor. Sounds to me like you have a problem of engine oil sucking in to the combustion chamber.

A more knowledgeable person may contradict or give better info. Sounds to me like one of those famous coincidences - you blew your tranny oil cooler (age/corrosion/?) and started blowing oil/diesel out the motor exhaust at the same time. The most common reason for black smoke is unburnt diesel fuel or engine oil - low compression (blown rings which is sucking up oil in to the chambers). Since you had low oil I suspect it is not a diesel problem (injection timing, injectors, etc). Low oil leads to high engine temp. Ideally you would like a warning for both high temp and low oil pressure. But high temp alarm is a good reason to shut the motor down and then you find out your oil is low.

Low raw water flow can cause overheating too of course - impeller/blocked coolers, etc).

You probably should get a mechanic to check it out. And don't run your engine at full throttle except for brief periods, or actually should say full RPM since that is what can cause the problems.
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Old 31-05-2016, 11:11   #5
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Re: Oil in raw water exhaust - trans oil cooler failed?

Thanks for the great reply! Much appreciated.

We were actually running the engine at about 2600 RPM, which is about 85% or so. With the prop/pitch we're running, we can only get up to about 2800. We had been running at that RPM level for maybe 3 or 4 minutes, and then hit a bunch of chop due to some power boats that sped past us. I had cut the throttle back to about 2000 as we pitched and heeled through the chop when we noticed the black oil or fuel coming from the exhaust. Engine had been running solid at about 180 degrees prior to that, with good oil pressure. We shut down right away and ended up sailing back to the slip. I checked the engine oil after it had been shut down a few min, and it was at normal level, black with no evidence of coolant, foam, discoloration, etc.
I am a trained diesel mechanic (US Navy), having worked on aviation ground support equipment, but not that versed with marine applications in particular, although I do understand how both cooling circuits work.
I did, however speak to 2 diesel mechanics this morning, and both thought the low oil pressure/high temp might be a temporary condition, and to crack the individual high-pressure fuel lines while the engine is running (assuming we get some oil pressure) to see if one of the cylinders is dead. Also to check for blow back from the oil fill cap. I'll check both. Good sign is that the engine did not seem to make any nasty noises, and it did start back up again easily after a few min, just to see if it would. It was still pretty hot, so we shut right down again.
I also have spare engine and trans coolers, and I'll check for oil in the raw water circuit before the injection elbow to see if the trans cooler may have ruptured. Not really any other way oil could have gotten into the exhaust. Could only be via a combustion chamber into the exhaust manifold, then straight out the elbow, or there would be oil through the raw water circuit if the trans cooler failed...

Thanks again!
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Old 31-05-2016, 11:31   #6
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Re: Oil in raw water exhaust - trans oil cooler failed?

High temp will cause low oil pressure.
What is the normal max RPM of your engine? If it's 3,000 then your not seriously over propped, but running 200 RPM short of max is running hard, which may lead to overheat if there is any weakness in your cooling system.
Source of "black oil" confuses me, what makes you think transmission cooler, do you have black oil in your transmission?

I'm thinking you ran her too hard, she overheated and maybe the black oil is mostly carbon and some oil that was in the exhaust system and the excess heat caused to break loose?
That is only if you can find no other source for the black oil. I'd start by checking exhaust elbow is not clogged, flushing out the fresh water cooling side, then cleaning the heat exchanger, cleaning out the raw water strainer and a new raw water impeller.

Sort of a shotgun approach, but I bet nothing is wrong with transmission, but you overheated the engine, hopefully causing no harm.
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Old 31-05-2016, 11:49   #7
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Re: Oil in raw water exhaust - trans oil cooler failed?

Top rated RPM for the W58 engine is 3000. I agree that the black "oil" may have been carbon build-up and/or fuel. In the moment, didn't have a chance to get a sample unfortunately. We were in a high traffic area of Chesapeake Bay at the time, and needed to get moving.
I had just serviced both raw and fresh water circuits - new impeller, coolant, hoses, belts, etc. a couple of weeks ago. The HX was also just cleaned out, acid-bathed and painted this last April. Only things that weren't replaced were the oil and trans coolers.
I think you may be correct on all points though. The boat is new to us as of last November. It had been sitting for 3 years prior, but our surveyor took her up to 2800 RPM for several min with no issues before we purchased, and the engine was just fully serviced, so I guess I assumed (aware of the implications ), that running her at around 2600 or thereabouts should be ok. Live and learn I guess!

Thanks for the input!!
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Old 31-05-2016, 11:57   #8
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Re: Oil in raw water exhaust - trans oil cooler failed?

Sounds to me that the oil cooler failed and not the transmission cooler. That would explain the low eng. oil. Happened to me bashing up the coast with a hurricane on my heels!
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Old 31-05-2016, 12:17   #9
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Re: Oil in raw water exhaust - trans oil cooler failed?

You may want to dive the boat, I've had once what looked like Oysters growing inside of the intake screen.
Last haul out I had mine replaced with ones that I can open and get the Oyster / clam / mussel, whatever it is out.

I think your overheating, 195 is absolutely normal for an automobile, but for instance my Yanmar's thermostat is a 160 or maybe 165.
Or maybe you have the wrong thermostat, you may have an automotive one?
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Old 31-05-2016, 13:12   #10
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Re: Oil in raw water exhaust - trans oil cooler failed?

If you're a mechanic, you should be able to make plumbing to pressure test your heat exchangers. I would temporally put in tees and install manual gauges to verify oil pressures.
Your engine (I think is the same block as a Perkins 4-135 and Mazda R2) is a natural - non-turbo. Also, Westerbeke is known for high prices. The issue with running at high hp is greater in turbo engines because of the much higher temps. I don't think the rpm you were running is an issue if the water and oil were kept cool enough.
Wrap rags, etc., around the injectors when you check the injectors. Usually on a 4 cylinder, a bad injector in very noticeable and power loss is immediate.
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Old 31-05-2016, 14:01   #11
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Re: Oil in raw water exhaust - trans oil cooler failed?

You say you experienced black smoke and overheating as well as "oil" in the exhaust at 2600 rpm (assuming the tach is accurate). Black smoke is typically partially burned fuel which can occur when the engine is overloaded. Overloading can also cause overheating. An overheated engine can show low oil pressure. The black "oil" could be crud that was blown out of the mixing elbow or muffler when the engine overheated. If you can't motor continuously at 2600 rpm, I'd suggest you check the prop for fouling, transmission for binding and engine/shaft alignment. Did the transmission cooler failure damage the transmission? Finally, the engine could be overpropped.
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Old 31-05-2016, 15:06   #12
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Re: Oil in raw water exhaust - trans oil cooler failed?

Thanks again for all the great suggestions and input. Much appreciated. To be clear, the boat was just launched a month ago, after being on the hard, during which time I replaced all the below-waterline thru-hulls and sea cocks. Also serviced the Maxi-Prop and had the hull and running gear cleaned up. As above, also had the HX reconditioned in April.
The smoke that came out at the time of overheating was pretty minimal. Slight black smoke with what looked like black oil in the water. Not sure at all that there was any real component failure. Was trying to logically figure out why oil would be in the raw water, and oil coolers seemed to fit the bill. Now I am getting a lot of feedback here, as well as from 2 marine diesel techs I spoke with today that the issue may well have been a simple case of overloading the engine, leading to overheat and low oil pressure. The engine oil cooler is in the fresh water circuit, so would not be a candidate. The thermostat is a Westerbeke part, and the engine running temp is supposed to be 180 degrees. I think it may well be possible that the prop pitch needs to be tweaked.

Again thanks!
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Old 31-05-2016, 15:39   #13
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Oil in raw water exhaust - trans oil cooler failed?

Your only 200 RPM off of max RPM of 3000.
I wouldn't mess with prop, your so very close, but running only 200 RPM from max obtainable isn't a cruise RPM in my book, that's running the snot out of it, that is 93% power, 75% is more like a cruise RPM to me, and that I believe is 2100 RPM.
For me, 75% power is a high cruise, Myself I cruise one closer to 60% . Noise is much less, fuel burn and range is much better.



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Old 31-05-2016, 16:00   #14
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Re: Oil in raw water exhaust - trans oil cooler failed?

Maybe it wasn't oil at all.

Once after months of day sailing and barely using the engine I needed to actually motor at cruise speed.

I had no idea the prop had become fouled like never before. The engine chugged out clouds of black smoke and unburned fuel in liquid form. Which was black as well and streamed in the water behind the boat.

Cleaned the prop and all was back to normal.


Edit to add...... I see your new post stating only slight black smoke. So I'm off base again. Though of course over loading does cause overheating.

Have you used the boat much since it's back in the water?

Problem started right away after all the work?
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Old 31-05-2016, 16:08   #15
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Re: Oil in raw water exhaust - trans oil cooler failed?

A64 - we were running at 2600 when the overheat happened, not 2800. I just said we ran at 2800 RPM during the survey, and that was the max attainable far as I am aware.
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