Oil sheen- do I chase this or forget about it?

Yanmar 6-LPA STP 2006 with 250 hours. Runs perfectly and to expected specs. Not smoking much beyond normal brief cold startup white.

I have noted a mild but noticeable exhaust oil sheen. It is not coolant. Oil and transmission fluid levels stay unchanged so far. Probably fuel- ran some exhaust discharge through strainer with absorbent pads and collected petroleum residue.


Notice it dockside at idle- seems same cold or warm. Can’t say at cruise.

Did disconnect air cooler warmer coils that are installed as an option to decrease white smoke warmup in off season on recommendation of many.

I installed new water pump, fuel cooler and tranny cooler this season as routine updates. No change in sheen.

Some posts I have read online say “live with it” as this is par for the course for this mechanical diesel- others say they solved the problem with injector adjustments or replacements, oil coolet replacements, and more.

Would you chase this further or not?

Unfair question. Most of us will not want to pollute. It does not seem possible to eliminate all from exhaust. Without seeing what concerns you how can I make a yes/no answer.

You are there. If you think you can reduce it then you must reduce it.

Exercise the boat, hard. Avoid dock idling. On a 15 year old boat 17 hours per year is not healthy. Do you have a water lift muffler that per chance is collecting diesel from numerous cold starts?

Soo-Valley: yes I agree and thus why I posted. Looking for advice if in fact the chase is at all worthwhile. Others have presumably been here before. Not a terrible sheen- but noticeable to me…. Maybe an inch wide at start- hard to quantify in words.

I will check the muffler.

Sunchaser: To clarify a bit- Boat is 1998. Motor is 2006 and delivered to me in October 2020 with 150 hrs-…. It is what it is. Since,I have put 100 on her this season and “run it good.”
Thanks.

If the sheen is unburned fuel, replacing the water pump, fuel cooler and tranny cooler would have nothing to do with this.

The only thing left is to have the injectors checked and adjusted or rebuilt as necessary.

Personally, I would ignore it and go boating. Mine seems to discharge a bit of unburned fuel as well but it has over 5K hours on it.

rwidman- I guess I do not know if it is fuel or oil… I am sure only that it is not coolant. I replaced the water pump, fuel cooler, and tranny cooler more as routine maintenance but alas it did not help.
( PS Would not a leaking fuel cooler or tranny cooler allow for a petroleum seepage in the seawater effluent?)

Thanks for your thoughts.

I have 3208T/As. When starting in warm weather not much smoke or sheen. In cooler weather I kill every mosquito within a mile circle. Don't worry about it. As stated run it.

Bonedoc said:

rwidman- I guess I do not know if it is fuel or oil… I am sure only that it is not coolant. I replaced the water pump, fuel cooler, and tranny cooler more as routine maintenance but alas it did not help.
( PS Would not a leaking fuel cooler or tranny cooler allow for a petroleum seepage in the seawater effluent?)

Thanks for your thoughts.

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If it is oil, the oil level will go down as you run the engine. If you are adding oil between oil changes, it might be oil. If not, it pretty much has to be fuel.

That makes sense…. No noticeable oil or transmission fluid level changes noted.

Whether you chase it depends on how much it bothers you and others. I doubt if it is hurting the engine.

But for those few hours I would strongly suspect injector fouling. Run it hard at 90% of wot rpms for a few hours and see if it doesn't improve. Watch the coolant temp and oil pressure carefully while you do this.

David

Alaskan Sea-Duction said:

I have 3208T/As. When starting in warm weather not much smoke or sheen. In cooler weather I kill every mosquito within a mile circle. Don't worry about it. As stated run it.

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lol, ME TOO!!! Installed block heaters this year. Now that the weather is turning, I will get a chance to test them...

Bonedoc said:

rwidman- I guess I do not know if it is fuel or oil… I am sure only that it is not coolant. I replaced the water pump, fuel cooler, and tranny cooler more as routine maintenance but alas it did not help.
( PS Would not a leaking fuel cooler or tranny cooler allow for a petroleum seepage in the seawater effluent?)

Thanks for your thoughts.

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I would think a leaking fuel cooler on this engine (I have same) would result in water in the fuel tank and not fuel into the higher pressure cooling water -at any speed/RPM. Also, remember at speed you are flushing almost 35 gallons a minute through there. The tiny bit (one inch) of sheen you mentioned probably would not bother you if you drank it. Ask me how I know, and I will tell you about being forced to drink/bathe in Navy Special Fuel Oil (black oil)-contaminated water while on "water hours" in the Tonkin Gulf.

Your mention of running the exhaust through a cloth makes me wonder if an oil sampling company like Blackstone where I have mine tested annually could take the cloth and tell you whether the petroleum in it is lube oil or fuel. Might be worth a call to them.

Thanks for your service. I was considering getting it tested somehow- I may make some calls as this would narrow down the possibilities for sure.

Thanks for the suggestions.

All mechanical injected diesels put some unburnt fuel in the exhaust at cold start and low load. And that slime can accumulate in muffler and exhaust tubing.

Worse on trawlers as they tend to just putt-putt along.

Agree with some hard running can tend to clean things out a bit. No need for full power, but maybe 70% power.

Fuget about it.

If after a few hard runs problem still exists it might be good to get valves and injectors adjusted. A mechanic that knows those engines may be able to help.

Scottwb96 said:

lol, ME TOO!!! Installed block heaters this year. Now that the weather is turning, I will get a chance to test them...

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Since I'm your next door neighbor I hope they work too.

Ok all tx for your interest and advise.
After traveling out of country past two weeks I got on vessel yesterday and pushed it for 90 minutes at 3600 RPM/20knts-(3800 WOT).
Sheen seems less…will report back in in near future.

Scottwb96 said:

lol, ME TOO!!! Installed block heaters this year. Now that the weather is turning, I will get a chance to test them...

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I think it should. Let us know.

"I got on vessel yesterday and pushed it for 90 minutes at 3600 RPM/20knts-(3800 WOT)."
Good looking boat! Downeast boats are tops for me @ those knots. Stable ride. Abit of a sheen will most likely stay,i've been living with one for years. I look / check it every trip and travel with confidence that all is stable.

We have had two 'sheen' situations. One was due to a leak in the fuel cooler. Fortunately fuel is under pressure and pushed outward, so no water into the fuel cooler. We also had a transmission cooler leak. That went the other way and required two oil changes to clear it. In both situations we had to replace the affected cooler.

It's bad form to knowingly leak oil into the water, and there's likely penalties involved if you get cited for it.

When injectors get old or damaged, they don't make a proper atomized mist. The bigger droplets don't completely burn and go out the exhaust, making a sheen. Sitting can cause rust in the injector nozzles that leads to erosion of the tiny holes in the injector tip. One of the reasons you should start the engine on some regular basis is to combat rust in the engine. You can buy new injector tips for most injectors and change them yourself. Or have a injector shop rebuild the injector. With a rebuild, the shop has equipment to verify the spray pattern.

Lepke said:

When injectors get old or damaged, they don't make a proper atomized mist. The bigger droplets don't completely burn and go out the exhaust, making a sheen. Sitting can cause rust in the injector nozzles that leads to erosion of the tiny holes in the injector tip. One of the reasons you should start the engine on some regular basis is to combat rust in the engine. You can buy new injector tips for most injectors and change them yourself. Or have a injector shop rebuild the injector. With a rebuild, the shop has equipment to verify the spray pattern.

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Can always count on your experience and help Lepke. Thank you.

phillippeterson said:

Can always count on your experience and help Lepke. Thank you.

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Got to agree !

"When injectors get old or damaged, they don't make a proper atomized mist."

This is true but atomized fuel is not what the engine runs on , its vaporized fuel that is needed, the tiny bubbles of fuel must first evaporate.

If they don't there will still be combustion from the droplet surface but it will be incomplete, the black smoke is partially combusted fuel,frequently called Bucky Balls.

Heat and time are the best way to gain efficiency, so a lower RPM with the same load (CPP prop?) helps all the fuel evaporate and be burned.

The newer 30,000 PSI fuel rail and electronic injectors allows 3 -5 shots of fuel per power stroke which heats the fuel better for more efficiency.

Oil sheen ? , too many factors to bother with unless you have to replace oil every few ours.

Forgetaboutit!

I haven’t read very many responses to your post so you may have already gotten this advice ,you have a turbo charged ,intercooled,high rpm engine .That’s designed to run at higher rpms at idle your turbo isn’t spooled up .And is probably running rich.If you’re worried about it.I have a technician plug his diagnostic equipment into it they can tell quite a bit especially what you’re injectors Are doing .otherwise unless you’re getting fuel in your oil I wouldn’t worry about it

It is either injectors or valves need adjustment

Thanks for all the responses- cruising back and forth to Ct this weekend and I will run it again at 3200-3400 RPM and observe. I may replace injectors over winter as this seems to be reasonably priced.

Bonedoc said:

Thanks for all the responses- cruising back and forth to Ct this weekend and I will run it again at 3200-3400 RPM and observe. I may replace injectors over winter as this seems to be reasonably priced.

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If you are going run it at or near WOT, do it under a load.