Oil slick from exhaust ?

[crg]

YANMAR 1GM10 / Sea water cooled.

Out for a nice sail last week, motored out of marina / bay as per normal all was well with the engine and cooling water from exhaust OK, on return back to marina engine started up OK, cooling water OK, just before entering marina noticed oil slick from exhaust !!! the smoke from the exhaust was clear as usual, lucky for me no one at the marina to notice the oil slick, got tied up OK and shut down engine ASAP.

Took a sample of the exhaust water to confirm that it was engine oil causing the slick.
Disconnected the cooling water feed to the exhaust mixing elbow and run up the engine for a few minutes, running the cooling water into a bucket to confirm that the water entering the mixing elbow was clean.

Looks like oil,s getting into exhaust chamber of the cylinder head, hopefully its just a leaking exhaust valve seal and not a crack or hole in the cylinder wall.

Is there any other way oil can get into the exhaust water?

Will take the valve cover off tomorrow to have a look at the valve seal.
Can the valve seals be changed out with the cylinder head left on the engine?

Cliff.

 

[starboard]

Could also be unburnt diesel, I have an old Volvo and if you over throttle I leave an oil slick behind of unburnt fuel!!! this is normal with these older engines!!

Paul.

 

[crg]

Thanks Paul,

The sample from the exhaust looks like engine oil, but you may be correct, I have access to a lab at work so will get it analysed to confirm oil or diesel.

Cheers Cliff.

 

[steve28]

Its most common for a hole to develop in the exhast port, it breaks into the section where the pushrods run.
You can find out if this is the case by removing the elbow.

 

[crg]

Thanks Steve,

Just removed the exhaust elbow, bloody big hole in cast wall between push rod and exhaust port !!!
New cylinder head required.

Cheers Cliff.