Engine oil in the water

[sgtnoah]

Through the summer I've been dealing with an oil consumption issue with my 2005 3.0L Mercruiser. I previously posted here and was given some great suggestions on things to try. Now that the season is over, it's time to get to the bottom of this one!

The issue: Oil consumption, 1/2 quart per 4 hours of running time. No smoke. On the hose, it will smoke very briefly at startup, but then the smoke quickly stops. No oil in the bilge. No water in the oil. Good power, good idle.

Steps taken so far: Compression check, all in range and within 10% of each other. Borescoped cylinder, no obvious damage. Inspected spark plugs, 3 have a nice even tan color, one is darker but not jet black. I don't think that it's black enough to explain this large amount of oil consumption.

Noticed a slight oily sheen on the water behind it. I'm not sure if it's leaked oil, or possibly the result of oily exhaust, or ???

This is where I am confused, I don't think valve guide seals (could they leak this much), or head gasket (oil doesn't have water in it), or even burning oil (spark plugs are not carboned up and black enough). Hmmmm, so where could this 1/2 quart per four hours be coming from?

Thank you in advance for your thoughts!

-- Pete

 

[alldodge]

If your not leaking it there is only one way, your burning it.

What's your serial number?

 

[DeepBlue2010]

Borescoped cylinder, no obvious damage.-- Pete

I am sure our experts here will put you on the right track soon enough. I am only trying to think out loud with you. With that said, what was the status of the piston tops on the Borescope? You said you inspected the cylinders but if you are burning oil, you will have a dark brown layer on top of the pistion. Did you notice any?