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Old 05-22-2019, 05:30 PM   #1
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Causes for gray smoke

Hi guys,

I can use some help to troubleshoot darer gray smoke from the exhaust on a new to us 41' trawler.
Engine is industrial Yanmar 145hp with a turbo born in 1987
When transmission is not engaged, I can give it a throttle to 2500rpm which is continuing duty Rpm for this engine and it's smooth and happy, no visible smoke.

When we are underway, anything over 1500rpm causes gray smoke and I did not try 2000 or over because the smoke does not look right and getting worse with more throttle and I can feel vibrations are increasing.

Am I correct assuming the engine is overloaded?
Maybe by incorrectly sized prop?

Can a missaligment in the shaft causes the overload?

Can it be a turbocharger not working correctly under the load or it engages with high rpm regardless of the load? I know nothing about turbochargers - this is a new kind of animal to me.

Anything you recommend to check first?
We are in the remote areas of Nova Scotia now and access to a mechanic is limited.

Thank you

Anton
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Old 05-22-2019, 05:53 PM   #2
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Black smoke - It could be over propped. but it sounds like the air fuel mix isn't correct. And that can be anything the puts too much fuel into the cylinder. Burned injector tip, turbo issue, restricted air intake, etc.
If it's blue smoke, that indicates oil burning - bad rings, worn cylinder, leaking valve guides, diesel in the oil, oil in the diesel, turbo leaking oil into the intake, and others.
It's easy to check alignment, loosen the coupler bolts and check the gap with a feeler gauge all the way around. If there's a too big gap at the top, the front of the engine needs to rise. Gap on the left, engine front needs to go left, etc. I do alignments to .002".
I'd call a major prop dealer with engine, transmission and current prop info and see what they say.
The turbo is controlled by the exhaust, but not designed for high rpm, no load. A failing bearing can cause turbo drag, less air, black smoke. If the engine has a lot of sludge buildup, the line to the turbo is one of the first places that get restricted oil flow. Low oil flow = bad turbo bearing, then bad seals, then oil in the intake, then turbo failure.
You gotta keep the oil clean in a turbo engine.
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Old 05-22-2019, 06:03 PM   #3
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Your getting good advice, so Iíll hit and run with a lucky guess. 1500 rpm is near the magic transition point where the turbo would start to matter. If you kept increasing throttle without further significant rpm increase and the smoke went from dark to black to streamers of carbon Iíd jump right to the conclusion that air was not keeping up with fuel. That is the job of the turbo.

Could be other things, but it would be on my short list to check first.

See what the blades look like, if they are clean or coked up. See if it spins easily.
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Old 05-22-2019, 06:12 PM   #4
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My guess would be that the turbo is not spooling up or you are losing boost pressure. You will get rated rpm with no load if the turbo is weak or not spinning at all. With a load on the engine (in Gear) you will get smoke and much less than rated rpm. Check hoses from turbo to manifold to be sure there are no leaks. Look for split hoses, loose clamps, and the like.
You didn’t state the make of the boat but some of the Mainship (Yanmar equipped) trawlers were known to have poorly designed exhaust systems causing seawater to back flow into the turbo.
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Old 05-22-2019, 06:21 PM   #5
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Thank you for your reply.
Oil was clean and I replaced the oil and filters recently.
I do not think turbo was serviced in 10 years or so.
Is there any temporary fix I can do until I get to civilization and have time to remove and clean it?
Some turbo cleaner spray maybe?
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Old 05-22-2019, 07:50 PM   #6
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Quote:
Originally Posted by Waterant View Post
Thank you for your reply.
Oil was clean and I replaced the oil and filters recently.
I do not think turbo was serviced in 10 years or so.
Is there any temporary fix I can do until I get to civilization and have time to remove and clean it?
Some turbo cleaner spray maybe?
Pop the air filter off and see if the turbo will spin freely with a socket and extension on the intake nut....might just be a little carbon/rust on the exhaust side blocking the blades. If you can't turn the extension by hand (no ratchet wrench), you'll need to pop the exhaust elbow off and clean the exhaust housing with PB Blaster, small screwdriver and vacuum until the blades will turn freely. Common problem on marine turbos that don't get run often.
Good luck!
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Old 05-22-2019, 07:58 PM   #7
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If the blades donít spin easily, well then you can run the boat at naturally aspirated speeds and just go slow for awhile. If they do, but are not clean, then you can clean them manually or you can even get the turbo spooled up a bit and spray some soapy water into the intake until it sputters a bit, then repeat. Personally, my guess is your beyond the spritzer solution and I fear you are going to find that the bearings are toast after sitting for a long time. Not my specific engine of experience, so canít speak at all to whatís common to find on your engine.

Iíve gone long distances with a bad turbo, get used to trawler speeds!
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