Another Smoking & Cruising Question

[Dockhead]

When we came to take possession of the New Boat, it turned out that she had suddenly started smoking like a chimney. A week of various mechanics later, no one knows why.

Here are the basic facts:

10 year-old Yanmar 100hp, turbocharged and intercooled.

830 hours

Starts and runs well. Produces full power and full RPM's.

Emits great clouds of gray smoke with a slight bluish tinge.

Smokes at idle and at load, cold and hot.

Did not do this before the engine was serviced (usual annual service plus replaced coolant, hoses, belts).

At the time of engine service, installed Racor fuel filter and had the old fuel polished (the polishers said that the fuel, although old, was clean, as was the tank).

The injectors weren't spraying perfectly, so I had them ultrasonically cleaned and set up. To be really sure, we tried the engine with a set of new injectors. No joy.


WTF? What could happen between two sea trials and an engine service, for this to suddenly appear? The experts are stumped; maybe one of your guys has a better insight.

[htraudes]

"Starts and runs well. Produces full power and full RPM's. Emits great clouds of gray smoke with a slight bluish tinge. Smokes at idle and at load, cold and hot" indicates fluid getting into exhaust. "Turbo & intercooled" adds options to what leaks.
Which fluid (cooling, fuel or lube)? What do you smell?

Where is the leak? Where fluid pressure exceeds exhaust pressure.

What has been dis- and reconnected during service? Gasket problem or bolts not well tightened.
I do not sus[pect core engine, but (connection to) peripheral equipment.

[Steve Thompson]

On a previous boat with a 200hp Volvo I had the same problem.After changeing everything possible turned out to be a slight internal leak in the intercooler.The build up of salts on the core limeted the airflow through the intercooler resuting in heavy smoke.The Volvo intercooler came apart and a radiator repairer fixed the leak.Not saying this is your problem just something to look at.
cheers Steve

[shakey doug]

restriction or valve off in injector fuel return line?

[Sailmonkey]

I have seen a turbo do this. These things like to be run, not idled. When the exh hits the turbo without a great deal of heat, the small passages in the turbo that keep exh pressure out of the oil gallery clog. then you've got a case of small amounts of oil in either the intake or the exh......turbo still works fine, just not as well as intended.

[Chief Engineer]

Turbos demand clean oil.......could be a bad oil seal in turbo....leaking intercooler.....
does the smoke have a sweet smell oil smell diesel smell?

Is the air restricted in the inlet side of turbo?

"A week of various mechanics"...that gets 'spensive after a while unless they work on a
"no cure no pay" basis

[Dockhead]

Originally Posted by Chief Engineer

Turbos demand clean oil.......could be a bad oil seal in turbo....leaking intercooler.....
does the smoke have a sweet smell oil smell diesel smell?

Is the air restricted in the inlet side of turbo?

"A week of various mechanics"...that gets 'spensive after a while unless they work on a
"no cure no pay" basis

'spensive indeed -- fortunately, I'm not paying for it, because I had not accepted the boat yet when the problem appeared.

We checked the intake tract -- no restrictions we could find. The first thing the first mechanic suspected was that the turbo was maybe stuck from disuse. Indeed it was a little sticky but not stuck, and after that we ran it hard and verified that we were getting good boost out of the turbo.

Smoke smells like diesel to me, but I'm not sure that's conclusive. One mechanic (a Yanmar specialist) started to think it might be oil smoke after all, after the obvious overfueling problems were excluded.

Turbo oil seal -- would that come on suddenly? Right after a service and oil change? I suppose that could be it. The first mechanic didn't think so, because he said that is usually associated with play in the bearings. In our case, there doesn't seem to be any at all.

The old oil was analyzed before the service and came out clean and with no unusual wear metals.

One reason why this is so mystifying is that the engine checked out so well during the survey and sea trials. On one of the two sea trials we even gave it a torture test at full revs -- 3800 RPM, for which the engine is not rated for continuous duty -- for 15 minutes or, with no heating whatsover, no complaints.

[Chief Engineer]

Was that 3800 in gear?

Did the owner take it up that high? Or did you?

[Dockhead]

Originally Posted by Chief Engineer

Was that 3800 in gear?

Did the owner take it up that high? Or did you?

Indeed. In gear, churning up a ferocious wake, and pushing the boat past hull speed to something like 10 knots over the water. I did it, with an engineer on board observing, and the owner's guy present, at sea trial.

That's the rated redline for the engine, not for continuous duty. Maximum continuous speed is 3600. Relaxed cruising speed is about 2500 which gives about 8 knots in calm water.

The prop is a just-overhauled Bruton Autoprop, which bites in really well (while pulling to starboard, however).

The engine seems to run fine, doesn't heat under any circumstances, makes full power, runs smooth, starts well. Just smokes like a barbecue.

[Chief Engineer]

Turbo shaft seals leaking

Turbo Oil Return Line clogged.

Note: The shaft of a some turbos don't have bearings per se...the shaft rides on a thin film of oil. This is under pressure....Overspeed the engine and you may blow a seal on an older engine.

Go over the list of what was done to the engine for maitenance...the answer might be right in front of you....proper weight oil for engine?

[Dockhead]

Thanks. But wouldn't leaking turbo seals produce distinctively blue smoke, rather than gray smoke with a blue tinge? Or can oil smoke look that way as well?

[Chief Engineer]

"Troubleshooting Marine Diesels" Peter Compton.

Originally Posted by Dockhead

Thanks. But wouldn't leaking turbo seals produce distinctively blue smoke, rather than gray smoke with a blue tinge? Or can oil smoke look that way as well?

[htraudes]

Just let the 'customer' talk, and all of a sudden there's a new fact that might be the key to the problem.......

[Dockhead]

Well, oil 10W-40, coolant changed, changed all belts and hoses, changed impeller, cleaned intake tract, looked at everything, installed dual Racor separator/filters.

I'm starting to think, though, that the problem may have begun with the sea trials and the running up to redline. The engineers said it was ok -- the engine is governed, and so forth. But we did run it at 3800 for 10 - 15 minutes, and on two occasions. I guess that could have popped a tubo seal or broken a ring, especially after a long lay-up?

Only problem is both of those things would point to blue smoke, wouldn't it? This smoke is more gray.

[Chief Engineer]

"White Smoke with a hint of blue indicates burned oil"

Page 43 Troubleshooting Marine Diesels Peter Compton

Page 408 of Calders' book goes into a little more detail...specifically redlining