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Old 11-01-2015, 11:04   #1
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unburned diesel in exhaust

We haven't wind or appreciable sunlight for a few days, so this morning I ran the engine for 30 minutes at 1,000 rpm to charge the house bank. I haven't used the engine to charge for years because we have both solar and a wind generator.

A few hours later, after weighing anchor, we noticed a diesel slick around us. Thinking this may have been the result of prolonged idling, I ran the boat at high rpms for about a mile, but the problem didn't go away.

The engine is a yanmar, turbo, eight years old with 700 hours on it. 4JH3TE.

Thoughts?


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Old 11-01-2015, 11:19   #2
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Re: unburned diesel in exhaust

Not good news. One thing could be a bad injector washing out one cylinder. I had that happen and the engine seemed to run fine on the other 3! Check that your oil level isnt getting fuller! Mine gained about a quart-1.5 quart in 8 hours of motoring... Incidentally, compression was low on that cylinder, but after fixing the injector and running a couple hours it came back. So I wouldn't run it too long until you figure it out....
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Old 11-01-2015, 11:19   #3
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Re: unburned diesel in exhaust

Leaking injector or bad turbo seal or a leaking oil cooler if it has one would be the three top choices. If the engine oil level stayed constant then turbo and oil cooler are fine. Then the injectors would be top of the list or very improbable rings.
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Old 11-01-2015, 11:35   #4
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Re: unburned diesel in exhaust

Or maybe not an issue at all. Calm water, running the engine mixes exhaust gas with raw water cooling. Sometimes the slick looks like diesel, but is just carbon floating on the still waters. Happens to us in Alameda occasionally. We're so used to it being windy here, we rarely bother to notice what's behind us.
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Old 11-01-2015, 12:00   #5
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Re: unburned diesel in exhaust

Hey thanks. Oil level seems constant, so I'm hoping its an injector. The boat's back in harbor, and I've just left off the keys with my mechanic.

This sort of thing happens every time I get enough money in the boat bank to buy an AIS transponder. I should have known better.

I'll post back once the mechanic takes a look.


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Old 11-01-2015, 12:35   #6
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unburned diesel in exhaust

Couldn't hurt to have the injectors tested and or rebuilt, when you say higher RPM, was that under a load? Usually a dirty injector cause a little more smoke and more of a Diesel knocking / clatter at idle, but they can do it so gradually, you don't notice.


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Old 12-01-2015, 10:42   #7
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Re: unburned diesel in exhaust

a friend had that exact same problem...white exhaust, meaning it was fuel going out the exhaust pipe, unburnt! went on for years, tried evrything, etc...started hard, ran funny, etc...sold the boat, new guy took it to a shop via a waterway, easier for the shop to get to it! well, it was a cracked head! found a used one, and never looked back...c
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Old 12-01-2015, 11:21   #8
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Re: unburned diesel in exhaust

Hi, Just a random note of information on Diesel engines...they like heat. So, when you decide to go sailing it is recommended to run them awhile at the dock so they get up to the proper operating temperature. Often times the cooling system needs the time to reach it's optimum temp. If you leave the dock and begin sailing in short time, then you right away shut down the engine, sometimes the "rings" have a tendency to "coke" up and after time.... they loose their ability to create good compression.....which is KEY to proper explosion within the cylinder. This is not gospel just information to pass on.
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Old 12-01-2015, 15:46   #9
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Re: unburned diesel in exhaust

Quote:
Originally Posted by Bash View Post
We haven't wind or appreciable sunlight for a few days, so this morning I ran the engine for 30 minutes at 1,000 rpm to charge the house bank. I haven't used the engine to charge for years because we have both solar and a wind generator.

A few hours later, after weighing anchor, we noticed a diesel slick around us. Thinking this may have been the result of prolonged idling, I ran the boat at high rpms for about a mile, but the problem didn't go away.

The engine is a yanmar, turbo, eight years old with 700 hours on it. 4JH3TE.

Thoughts?


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I was told by an old time Perkins diesel mechanic to always operate the engine under load. If at the dock put it in gear to give it load against the mooring lines. Even if you are running to charge while sailing keep it in gear.
His second gem was that if you start your engine make sure you run it until it is HOT before turning it off. His final gem was don't let anyone touch the engine until it has 10,000 hours...then only do the top end.
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Old 15-01-2015, 22:05   #10
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Re: unburned diesel in exhaust

Years ago I had a 120 hp Ford Leaman that had a similar issue. It turned out one of the rocker arms was incorrectly adjusted (too tight) which did not allow enough compression to be built up in that cylinder to combust the fuel so the unburned diesel went out the exhaust and left a sheen in the water.
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Old 16-01-2015, 10:13   #11
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Re: unburned diesel in exhaust

Good point, I had a 4 cyl Perkins that one push rod came off the rocker... that engine left a diesel slick on the water also. Actually didn't run that bad!
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Old 16-01-2015, 10:17   #12
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Re: unburned diesel in exhaust

It's called wet stacking. When a diesel engine is run for long periods without a proper load, unburned fuel can collect in the exhaust system, eventually finding its way to the end of the exhaust pipe. You need to make sure to run the engine under load - to do otherwise is hard on it.
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Old 16-01-2015, 11:51   #13
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Re: unburned diesel in exhaust

My guess would be a lack of compression for whatever reason, resulting in no ignition. Blown gasket, worn piston rings, worn cylinder liner, leaky valves, cracked combustion chamber etc.

I'll be interested to know the actual cause once the mechanic has made a diagnosis!
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Old 16-01-2015, 15:01   #14
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Re: unburned diesel in exhaust

I love all the dire predictions being mentioned here. I wonder if some folks are actually hoping there is a problem - misery loving company and all.

My brother ran the tractor to operate a hydraulically powered log splitter. Previously, the diesel engine was having no problems. Afterwards, he noted oil leaking out of the muffler. There was no loss of power, no different engine noise, no loss of crankcase oil. He had been running the engine with minimal load for about an hour. I told him to get a smaller tractor! Actually, he ran the engine at a higher RPM the next day and the problem resolved - but it took a LONG time to clear the unburnt fuel from the muffler. If you still see a slick after running the engine for 3-4 hours under load, I would worry more.

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Old 16-01-2015, 15:23   #15
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Re: unburned diesel in exhaust

CraztOldBoatGuy ! I could not agree more! This used to happen all the time especially in winter for us, when we left the engines running in our trucks while loading and unloading to keep the cab warm. It was really noticeable after waking after our 8 Hrs. of sack time. We could make it a little less noticeable buy running the engines at 12-1300 rpms, but then you would burn more fuel !
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