while changing my impeller in a 1969 105 I noticed some oil residue on the impeller. Is this anything to be concerned about? No oil under the pump housing so I think it's from the exhaust.
Then the gearcase should be fine. You might want to check for a misfiring plug or a weak ign coil. This might be causing the oil just above the waterpump.<br /><br />TMD
The most common reason for oil on the impeller is a bad upper drive shaft seal but there is a small hole drilled on the top of your water pump housing to let air escape to prevent cavitation of the impeller. it is not uncommon for unburned fuel and oil to drip down the chamber and get on top of the water pump if this happens a black oil film could possibly go through that small hole into the impeller. I have never seen this happen, but i can theorize it. good luck, bret <br /><br />If you need further assistance please email me @ forcepower01@yahoo.com. thanks,Bret