slight oil slick in diesel engine exhaust
This from a google search cuz I was curious, I can claim very little knowledge on my own:
Symtom:Unburned engine oil in exhaust:
1)Leak in oil cooler.
2)Bad shaft seal on raw water pump.
3)Could be fuel, not oil ?
This from the site: http://www.geocities.com/bill_dietrich/BoatEngineMaintenance.html.