Mercury 20 HP Lower unit shift shaft problem

[mmf]

I am stumped on a problem I ran into yesterday when putting on a lower unit on a late 70's model 20 hp motor. I bought a used parts motor that had a supposedly good lower unit awhile back, I removed the lower unit frome the parts motor and put on new water pump etc, replaced lu fluid etc and checked operation of shift shaft and observed from overhead view, full clockwise is reverse, one click counter-clockwise from reverse is neutral and one click counter-clockwise from neutral is forward. I installaed lower unit on receipient motor while everything was in neutral, after I got it on, I shifted motor lever into forward, and the lower unit was in Reverse! and reverse was Forward! I pulled off to check over and over again several times and cant figure this one out. The shift shaft on the lower cowl of the motor turns clockwise to go into forward and counterclockwise to go into reverse when viewed from overhead (looking at gear) this is opposite of the way the lower unit shifts! Is it possible someone has put the shift lever ramp on the wrong side? It does not look like anyone has ever been into the lower unit before! I checked a little 9.8 HP merc lower unit I have and It shifts the SAME way as the used 20 HP lower unit does! Any help or comments? THanks!

 

[mmf]

Re: Mercury 20 HP Lower unit shift shaft problem

well, i dont think it matters much now, my curiousity led me to tear down the lower unit too see what was going on and alas another STUCK bearing carrier, had to destroy the housing to get the carrier our without damaging it since these are the parts so hard to come by and the gearcase nut too! Looked down inside to shift cam and the ramp appears to be very short on the high side???? I still need to remove shift shaft to get it out and I will report my findings, I did find some rust and corrosion on the bearing next to the shift shaft, maybe it has rusted and corroded, I will see shortly!

 

[mmf]

Re: Mercury 20 HP Lower unit shift shaft problem

Found this out reading my old Clymer manual about the 3.9, 4, 6, 7.5, 110 and 20 HP model lower units and I will quote on the installation of the shift shaft cam, " Install the shift cam into the gearcase. Notches must face up and to the left when seen from the skeg (the cam works to the left on 1964-1970 models and to the right on 1971 models)." (My Clymer manual covers only 1964-1971 models)........
So evidently, the shift shaft works OPPOSITE from pre 1971 verses 1971 UP models in the small HP lower units. I checked the serial number on my donor motor lower unit and indeed it was a 1970 model and I am trying to put in on a 1977 model motor so, BE INFORMED of this if you buy an older lower unit to replace your bad one!!!

 

[Sunfish12]

Re: Mercury 20 HP Lower unit shift shaft problem

That's too bad about that parts lower unit, someone could have used it.

 

[mmf]

Re: Mercury 20 HP Lower unit shift shaft problem

Oh, I am going to use it, only the housing is busted, I have three nice housings, this one looked to have been run in salt and every one I run across that has been dipped in salt will NOT co-operate with the standard tear down procedures. The bearing carriers REALLY get stuck on these. I have all necessary tools etc. and I work on these smaller motors alot, especially the 20 HP motors. If I ran one in salt that was in good shape, I would tear it down at least twice a year, just to relube joining parts etc, especially the driveshaft splines, you just don't know the number of salty motors I have bought that the driveshaft was stuck into the crankshaft and impossible to remove! I have had to bust the exaust housings on many and weld steel plates on the driveshaft to hammer off the LU on some motors!