Friend has an older baja that is leaking what looks like oil out of the starboard thru hull exhaust. When hooked up to a hose and idling, no apparent oil is coming out, which tells me its a very minute leak. However, after running it on the lake or at the house, he gets a oily dripping stain from the exhaust...several different issues I'm sure it could be, but was unable to google or yahoo this exact problem specifically...only searches of water getting in the oil, not oil getting in the exhaust after letting the boat sit.

He knows he can take it to the nearest certified mechanic...blah blah blah...just trying to do a bit of problem specific research before hand. Thanks.

could be valve guide seals on exhaust valves leaking.

Does the motor have an oil cooler?.If so that would be my first guess.

No oil cooler. It is a mid to lower 90's 350 chevy motor. It just started doing this during the last month. Not too familiar with the valve theory...could you elaborate a bit on it?

Make sure your oil isn't milky which it doesn't sound like it is. I would say a bad valve seal or seals. At idle you don't get a lot of oil on the top end however running higher rpms also increases pressure and pumps much more up top. Pull the valve cover off the side your getting the leak and see what's going on. If you have the ability to pull the springs on that side do that also to see if you have the correct stem/guide clearance.