Reply To: 1958 Johnson Gearcase

[Mumbles]

A ’58 to ’63 QD or Sportwin gearcase is a straight bolt on job. No machining required as would be the case trying to fit a CD or AD gearcase to the ’58 QD. The smaller horse gearcases would need the lower driveshaft bushing reamed out to accept the larger ten horse driveshaft and then there’s no guaranteeing there is enough meat in the CD/AD gearcase bushings to do it. Then you’d have to make sure the ten horse gears will fit into the CD/AD gearcase as some pinions were key driven and others were splined, depending on the year.. It would probably be easiest to cut both driveshafts below the powerhead and splice one together with the correct spline on top to avoid any problems with the gears, water pump, and bushings. Then the $64 question is, are the bolt patterns to the exhaust housing the same? They look the same, but are they? I know the skeg bolt patterns look the same between the two models but they are slightly out of alignment to each other.

I did use a later 9.5 horse gearcase once on a QD but it seems to me I had to switch some internal parts around to make it work. Can’t remember exactly what I did as that was a few years ago now.