The mystery oil slick in exhaust


I'd like your opinion on this engine issue.

When we bought the boat in 2012, about every 30 seconds you could see a drop of oil come out from underwater, on the boat's exhaust.  Like a flower opening, you saw a dot which then became a small circle.  The engine had 2000 hrs.

The engine now has 3,525 hours.  Some people think the white smoke that comes out of it is normal, but I think it is a bit much.  But what worries me is that the oil in the water is not acceptable.  I am pretty sure the other boats don't do this.  Look at the attached photo, taken 5 minutes after the engine was turned off.  Zero oil on the port side, and zero oil around the surrounding boats.

Some stats from the last 58 hours of engine use (from eastern Crete to Hyères, with stops along the way, 1171 miles if we had motored in straight lines, but we obviously sailed most of the way):
 - fuel consumed: 310 liters (includes 6 hours of genset use at 3/4 load)
 - oil added: 1/2 of 1 quart

Many thanks in advance for your thoughts.  I've asked for a mechanic to come by to see the 100HP Yanmar.


SM2K N. 350 (2002)

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