oil in engine exhaust

[oded kishony]

Greetings,

I've noticed that when I push the throttle on my Yanmar 8HP 1cyl Diesel engine I get what appears to be black oil coming from the exhaust. The engine starts right up and does not smoke at all. It also does not seem to be consuming oil from worn rings etc. Is this normal?

Thanks,
Oded Kishony

[Fortis]

It could be growth in your diesel tank, reducing the ability of the engine to explode the diesel fully, thus you are getting the scorched diesel remains...which basically look and smell just like sump oil.

Option two is that you got a diesel that has been contaminated with distilate (happens more often then you might think). While the two are almost the same thing, you will get a bit of waste sludge in the exhaust. This is sufficient to kill a car or light truck after a while, but in a boats much more open exhaust system it just flies out the back.

As a last possibility, you may want to just get the engine a minor service so they can optimise fuel flow/combustion.


Alex.


Alex.

[Parrothead]

I agree with Fortis. Problem sounds simple cuz your not burning oil.....use a outboard pump siphon hose or what ever you have and put a quart of your fuel in a clear glass jar and let sit for at least 24 hours. Any fuel issue should be easily seen at the bottom.

[oded kishony]

Thanks!

I recently bought a Bahama fuel filter and am planning to polish the fuel and try to clean the tank. Perhaps the best part of valor would be to simply replace the fuel and just for good measure filter the new fuel. I use so little fuel that I think most of the diesel in the tank is at least 2 years old. I've added biocides to it.

Thanks again,
Oded Kishony

[Fortis]

The bio-cide is the likely problem. If you had a heavy infestation of the critters that grow in diesel...And you killed them all off...and then maybe filled some more fuel into the tank, or just had a really rough time where the boat got shaken up more then usual...then the dead bodies of the billions of critters you murdered have been swished away form where they had clung in life (the air/fuel interface line) and their itty bity corpses have been flushed down to the bottom of the tank, where your  intake hose is.

Just changing out the fuel will not help much, as the sludge will still be in the bottom of the tank. Just polishing the new fuel coming in will not help much as the sludge will contaminate the new fuel once it reaches the bottom of the tank...
You get the idea.

Cleaning out the tank, will work.


Alex.

[Ol' Coot]

Oded,

Is the exhaust exhaust dark all the time or just when you throttle up?  If it's only as you are starting to put load on the engine you may not really have a problem.  Watch an 18 wheeler out on the highway when he's accelerating.  Every time he up shifts and puts a new load on the engine, you'll likely see a blast of black smoke from his exhaust.  Diesels do that.

Kevin

[oded kishony]

> Is the exhaust exhaust dark all the time or just when you throttle up?<

No black smoke at all. Only when I push the throttle wide open do I get an oily black liquid coming out the exhaust along with the cooling water (raw water cooled)

Any ideas of a legit way to dispose of old, possibly polluted, diesel fuel?

Oded

[AdriftAtSea]

Yes, you can take it to a fuel dealer, and they have to accept the old fuel. Same with used motor oil.

[Captain Smollett]

Any ideas of a legit way to dispose of old, possibly polluted, diesel fuel?

Burn it in the fall when you burn your leaves?  Much safer than using gasoline for that purpose (which a lot of folks do around here).

[BobW]

Burn it in the fall when you burn your leaves?

Burn leaves in the fall?  Not here in California!  Not anymore.  And certainly not with diesel fuel or gasoline.  We're lucky we're still allowed to use those fuels in cars and boats. ;)

[Zen]

How true, how true!

[rtbates]

If it's black NOT blue then it's probably excess diesel not oil. Most likely or at least the first try might be simply to run the motor more and harder. When I bought my Cape Dory 25D, which has teh 6.5hp 1GM, the exhaust would emit black soot at anything close to 2k rpm. several hours of motor sailing cured it. Speaking of the 1GM, when was the last time you checked your exhaust elbow? I just replaced my 1GM's head because the previous owner went years with a corroded exhaust elbow. You'll never know when the exhaust elbow corrodes through allowing sea water to enter the exhaust port. As long as the motor is running the exhaust pressure keeps the water moving away from the exhaust port. But as soon as you shut her down water will settle in the exhaust port. Over time it corrodes through the exhaust port into the pushrod tubes. Mine had holes through both the intake and exhaust side. I guess that's why Yanmar lists the exhaust elbow as a 'spare part' that should be carries along with impellers and belts.

Good luck

Randy Cape Dory 25D Seraph