slight oil slick in diesel engine exhaust

[mcagney]

I have a Volvo Penta MD17D (3 cylinder 36HP raw water cooled diesel) that is running perfectly except it is consuming approx one quart of engine oil per 20 hours of operation. The oil in the crank case is clean (not the usual black I would expect from a diesel – no sign of any water intrusion) and the engine always starts first time (without any glowplugs) so I know compression is good. This would suggest (at least to me) that since there is no water leak into the crankcase or soot being deposited (engine oil is not turning black) I don’t have piston ring wear or head gasket leak. However I do observe a very slight oil slick in the cooling water discharge in the exhaust. My question is where is the likely oil consumption leak? Could it be something as simple as a leaking seal in the water pump shaft allowing crankcase oil to enter the cooling system (but not the other way round). Any suggestions as to what I should look for. The engine is 20 years old (don’t know the engine hours).

[p32]

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.