Shamus, Forgive my shaky memory but a year or two ago I had two 54 Evinrude 25 HP . One Evinrude was a parts motor and it had the electric start. The other running motor did not have electric start. I figured I could maybe use the bracket, flywheel, and hood from that motor and put electric start onto the running Evinrude. The bracket is supported mostly by one long bolt that screws into a boss cast onto the powerhead . There was no boss on the non electric motor to accept the bolt. I concluded that electric start motors were built that way at the factory and no backfit was possible for 1954 Big twins.
I hope another member chimes in to correct me but I expect that Johnson could be the same. Take a good look at the powerhead photos. The added boss has a qtip in the hole. .
