Ran our recently purchased 1983 Hunter H34 for about 2 hours on Monday to get the feel of the handling and to practice docking in good weather. Today when I went to work on another issue. I checked the engine (3GMF Yanmar) I noticed that there was oil leaking from the top of what I would call the rocker arm cover on a gas engine. There is a round raised spot near the compression release levers and the oil seems to be leaking from that area. In prepping the boat the broker painted over the engine so can’t tell if it was a rust area or not. It was not leaking there before and we have run the engine a number of times. Today when I found it, it had been running for about 30 mins at the dock. Any ideas or suggestions, I'll probably need to replace the cover but was wondering what could have been a cause. Any ideas?