Home › Forum › Ask A Member › RD-17 Compatibilities? (Johnson 1955 25hp) › Reply To: RD-17 Compatibilities? (Johnson 1955 25hp)
You can use a powerhead frrom ’56 30 HP or 57/58 35HP. The powerbeads from the Gale built 40HP motors will also bolt up, but it must be a gale unit that is not a “super Quite” double wall exhaust leg. The ’62 and up motors had a bigger top end on the crank and will require you to use the flywheel that came with that engine.
The 5 HP increase from ’55-’56 came from a few places. Compression was in crease from 5:1 to 6:1. The area of the holes in the reed plate was also increased. Carns are the same. the 30HP pistons have the deflectors clipped off at the edges to work with teh higher compression head. Adding needle bearing to the small end of the rod also helped.
The earlier 25 HP powerheads will work, but were usually unpainted and had the cable setup for spark advance. You can swap over all of the accessories and make it work.
What is wrong with yours???