Burning Oil

[36041]

All,

One of my 3 year old Yamaha 9.9's is going through it's .75 liter of oil in about 6 hours of hard running. It's not leaking out, so it must be burning. The engine runs smoothly and makes normal power, so my thought is either a valve seal is leaking or maybe a piston ring is busted. When we get down to the Exumas and are going to be stationary for a couple of weeks I plan on pulling the engine and finding out whats wrong. Anyone have any suggestions they'd like to float? All ideas are apreciated.

Regards,
Tom
36041
http://www.tendervittles.net

[amytom]

Tom,

If it's burning oil pulling the plug will confirm. The times when I've seen broken rings the compression is usually quite a bit lower; I would expect to see some performance loss. If the valve seals are toast you might be able to fix without pulling the head. I would suspect and try the valve seals first.

Also, if the plugs look clean you may still have a leak between the oil pan and the water / exhaust passage, might not be readily visible. The fix for this would probably involve pulling the power head from the frame.

Hope this helps

Tom

[Allezcat]

Tom
I suspect Amytom is right. I have had several older engines leak oil out the corroded oil pan which then drips into the exhaust passage and shows up underwater at the exhaust outlet. When the engine is in the water in calm conditions, look for a sheen on the water surface near the lower unit. The fix does involve removing the powerhead, not a fun job.
Chet
Allezcat 36010

[thinwater]

I had the corrosion variant. Normally, the sheen was not visible. It would not loose much oil sitting, even for weeks, but it would loose it withing hours running.

I discarded the engine. Not worth fixing, IMHO. It was old.

Either way, if you are loosing oil fast it is EASY to seize and engine. I would just run on the other engine, except for docking, until repaired.