Many thanks for all of the suggestions and hints.  The oil leaks slower than I said and a drip every 4 hours or so also comes out when the engine is off.  The total leak in 10 days is about a fifth of the way between the Max and Min marks in the reservoir.  I identified the source of the leak: it is the junction of the part (coupling?) that you can rotate by hand when in neutral between the reverse gearbox and the upper C-drive, right against the C-drive. 

Craig, it sounds like this is the upper shaft seal you mentioned.  The procedure you described (scoot the engine back a bit) is beyond my capabilities, so I will have to get a mechanic.  Can the procedure be done with the boat in the water?  (I have a vacuum pump to suck the oil out.). Is the 60-90-10 seal easy to find? Any additional specifications for it (temperature etc)?  It would have been cheaper to install a rope cutter....

I really appreciate all the help.  This year the maintenance time has been high.  I had 8 pumps fail, needing replacing or servicing, and 2 major problems with the generator, as well as preparing the boat for my first Ocean crossing ever (Atlantic early December), so I have been very busy ... like the rest of you I guess.

Eamonn Washington
Travel Bug
Super Maramu #151
Currently in Calasetta, Sardinia, Italy.