i've got a '74 140 h3. i check the engine oil on it before i start it up and when i refuel. usually it doesn't use too much, it certainly doesn't blow clouds of blue smoke or anything. however, i was out puttering in the garage today, and decided to take the two shields off of the engine and get that mouse nest out from behind the cylinder there. noticed oil on my (engines) head. after retightening the headbolts, some which were loose, and some not at all, is there anything else to be done about this oil outside the engine problem? what is causing that? i pulled the plug and the little bit that i can see in there looks clean enough to eat of off. is this going to need a head gasket, or worse?