I have an old 60's vintage Johnson outboard.  It's been a reliable machine up until recently.  But lately, I've noticed that what must be lower unit oil is dripping down from a not easily accessible portion of the motor (between the lower unit and the motor itself).  Are there any outboard guru's out there who recognize this problem? Is this likely a seal/gasket problem or can I expect something worse?  I expect I'll have to take it in soon.

It is a problem you can probably  fix yourself.  There are multiple seals and gaskets that could be the problem.  But you should just replace them all.  Post a messeage on the link I attached below.  You will have a parts diagram and anything else you need within a couple minutes depending on the time of day.  you can get a seal kit for around 20 bucks at NAPA.  If you dont like working on stuff I am sure you can take it in but this time of year I would just try doin it yourself.  You could build a pressure tester using a lower unit oil fill screw and connect it to a air compressor at 5-7lb of pressure and spray soapy water on the lower unit to see where it is leaking from.  But replacing all the seals should be done as well.  Good luck and like I said post on the link below and you will get detailed help.  

http://www.aomci.org/cgi-bin/yabb2/YaBB.pl?board=askamember

What's the lube like in the LU?  Is it low or getting that milk chocolate color from water?  If full and not getting water, it's probably just the exhaust causing the black oil.  

I find it highly unlikely the gear lube in the lower unit is coming out of an area above the lower unit. Like way2slow said its probably unburnt 2stroke oil.

X3 on the exhaust oil. I thought mine was doing the same thing...until I figured it out.

I find it highly unlikely the gear lube in the lower unit is coming out of an area above the lower unit. Like way2slow said its probably unburnt 2stroke oil.

I considered that it could be unburnt 2 stroke oil but would it still be greenish and fairly clean in appearance? I did change my lower unit oil not long ago (thinking the leak would mandate a refill) and the oil was clean (not milky or watery).  I can't tell if it's measurably low in oil without comparing the amount in it now against what it takes to refill it.  There is no dipstick (obviously).

Alot of 2 stroke oils are blueish green also. What does it smell like?

If its got a gassy and/or burnt smell: 2 stroke oil, no worries. If it does smell like the gear oil you will have to get it fixed, and is probably the upper shaft seal or something like that.