Sudden oil sheen from Yanmar?

[OrangeCrush]

I'm halfway through a 6 week cruise and I just noticed a new oil sheen coming from my exhaust flow (Yanmar 4Jh5E with low hours). I've been motoring a good amount on this trip (4 hours today) but nothing too demanding. As per the manual, I'm in the habit of cycling the motor from low to high throttle 5 times before cooling/shutting down to burn off carbon. I never saw a sheen before today and I would have noticed it, but the fluid levels are still good and there are no changes to motor sound or function. Any idea what could suddenly cause a very light but visible oil sheen?

[a64pilot]

A dirty fuel injector gets my vote for the issue.
As opposed to running it up a few seconds in neutral, I run mine hard for a couple of minutes towards the end of a day of motoring.

[Lepke]

Sudden is usually an injector.

[OrangeCrush]

How concerned would you be about it? I don't feel confortable doing too much tinkering myself this far from home, but I could find a local mechanic to look at it...

[a64pilot]

Wouldn't bother me much at all most Yanmars have a reputation for being a little smokey, and a slight sheen and smoke both can come from just a little unburnt fuel.
Unless of course she started smoking a lot.
I'd run a can or two of sea foam in the tank, depending on how large the tank is, that may well clean it up if it's just varnish on an injector tip, which it may well be.

If you don't know how long it's been since the injectors have been cleaned and pop tested, once I got to a good place to have that done I would

[OrangeCrush]

Sounds like a good strategy, thanks a lot for the advice

[Cheechako]

I had a Perkins doing that. Turns out the pushrod had come off the rocker so one cylinder not working. You really couldn't tell it on a 4 cylinder engine. So watch your oil level, mine got higher and higher as the fuel was being pushed past the piston rings into the sump due to the valve not opening...

[model 10]

This is pretty funny that you only had a 3 cylinder engine and didn't know it. How long did that go on? I remember you once saying your boat only used something like .6 gal per hour. I think this might be it.

[OrangeCrush]

I'm in a very salty little town here in Lunenberg, Nova Scotia. If I'm lucky I'll find a good mechanic to clean the injectors tomorrow.

If I end up going the Sea Foam route, maybe it would make more sense putting it directly in the fuel filters? Higher concentration to the injection system and less tank sediment to dislodge. Thoughts?

[Cheechako]

Originally Posted by Guy

This is pretty funny that you only had a 3 cylinder engine and didn't know it. How long did that go on? I remember you once saying your boat only used something like .6 gal per hour. I think this might be it.

Haha, yeah this is a different boat. This was the little 32 ft Trawler I had. It was surprising it wasn't more noticeable. The engine started right up and seemed to run well, however it was a 4-236 in a 32 ft boat so a bit overpowered. You can imagine the surprise when we took the rocker cover off and the pushrod is sitting there alongside the rocker! I'm not even sure how that happens or that it was possible. I guess the pushrod can bend enough to do it without permanent deformation. "springy". We reused the push rod as it was perfectly straight! We were on a trip south in Fl so I was checking the oil every morning... and it was getting fuller and fuller!

[carlylelk]

If the sea water goes through a transmission heat exchanger, check your transmission fluid now. If the transmission heat exchanger has a hole in it, it will suck the transmission fluid out of your transmission and burn it up.

[a64pilot]

Valve sticks open and push rod falls out of the rocker pocket, next time piston comes up it closes valve.
You got lucky, I've seen more than once when the piston pushes the valve closed it bends the valve and the valve head pops off and trashes that cylinder.

[a64pilot]

Originally Posted by carlylelk

If the sea water goes through a transmission heat exchanger, check your transmission fluid now. If the transmission heat exchanger has a hole in it, it will suck the transmission fluid out of your transmission and burn it up.

That is an idea I hadn't thought of but it sure is possible.

[a64pilot]

A closed valve on an engine will make that cylinder actually work like an air spring and it will run smooth. Back in the 80's I think Cadillac had a V8 engine that would shut down two and run on 6 and even shut down 4 and run on 4. It did so I believe by disabling the valves in the shut down cylinder, if the valves still worked then you would of course have an air compressor and that takes bunches of power to run, but close the valves and you have an air spring.

[Crew of Turning]

Should not be a problem finding several well skilled diesel mechanics in Lunenburg N.S. it is of course a working harbour first and and a tourist harbour second. Is the Bluenose there now?