Re: Old 3 HP Johnson Sea Horse
Is he changing the gaskets on the drain and vent screw every time? That is the number 1 spot for water intrusion. If not I would replace them, then run it again to determine if the leak is fixed. If there is still water intrusion, he will need to pressure test to determine exactly where the leak is, or simply replace all the seals. Steve will definately be 1 of the guys to talk to on here about the older motors. Good luck.
Just for future....
To pressure/vacuum test a lower unit:
a) drain the gear oil
b) use an appropriate adapter with a gauge tee'd in to apply pressure or vacuum. No more than 15 psig for pressure. You can use a bicycle pump or any other compressed air source for pressure. For vacuum, you need a vacuum pump.
c) LU should retain some pressure or vacuum for 45 minutes minimum.
d) If pressure doesn't hold, submerge LU in water to find leak source [possibilities: drive shaft seal, prop shaft seal(s) (usually two), shift shaft seal and the fill/drain screw washers.]
e) replace offending seal(s) as required.