72 Johnson Hydro Electric Slow Reverse

I have a 72 Johnson 65 hp, Since I bought it several years ago the reverse is hardly existant - about like a trolling motor in speed 1. There is no noise and when the motor is out of water it appears as the reverse works fine. The voltages are right on the wires and the oil in the unit was recently changed using the johnson premium oil. The foward works well. It does seem however that the reverse works a 'little' better than it did at first in that I can manuver very slowly as long as there is no wind or current. Could it be that the previous owner used the wrong oil?. I'm hopeing that I don't have to take this thing apart. Any suggestions?

there is a chk ball ,in that pump,that when it wears and bleeds past,can cause sluggish rev and neutral,...and an o ring around a plunger that can lk.....just a cpl of things that come to mind,and would require a complete disassembly,.....if....u can find anyone that knows how to service it any more...u may have to do it urself,....but,....it would have to be a really good eng before i would attempt repair....if u get into the late 70's,or ltr,..u r waaaay better off...

The first time an answer that makes sense. I'll probably just deal with the slow reverse unless I can find a used lower unit, I saw some on Ebay described as belonging to a 1972 60 hp johnson - Was there one? I only saw 71 60hp Is there any referance to what years and hp the lower units can be interchanged? I think the only reason I really want to save this one is because of the 50 year anniversary series, if thats any consolation.