Re: Honda 90 oil leak
Could be leaking from water pump base gasket/o-ring, drive shaft seal, or shift shaft seals. All are easy to replace and located on the top of the lower unit.
Look at boats.net to find a parts illustration of your motor and you should see which seals/gaskets may be culprit.
I'd order and replace all of them, they are not expensive.
If you can remove your lower unit from the motor you could probably change these yourself.