1974 to 1980 Johnson

Just a thought that I would like to pass along for ideas. I have both a 1974 and a 1980 Johnson 9.9 outboard. The 1980 has only 30# compression on the bottom cylinder and 90 on the top so its pretty well shot. I am thinking as long as I change out the complete ignition system I cant see why I couldn't put the 1974 powerhead on the 1980 motor? The 74 the only thing that is good is the powerhead on that one. Tiller handle is broke and lower unit is shot. Recoil, carb ect should change out I would think.I think the only part of the block I would have to change is the cover that the cdi box bolts on and that looks like no problem. Would it work or am I way off. Don't want to start on it to find any major no goes LOL. Thanks, Jim

I don't see why it won't work. Motor is all the same more or less. Only changes are thermostat and pee hole.
The shaft should be the same. Its a 2 stroke. I've read some folks have done the conversion of point to cdi. I actually like the old points motors.

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Think I will go for it then as it sounds like a good project for this upcoming fall. I have a few projects going now and got to take some time to go fishing so this one can wait a bit. Thanks, Jim

Decided to do it now and everything went good. I tried using the old exhaust gasket and it worked ok the first time. I ended up having to pull the powerhead partway because I had a thermostat gasket leaking and was just as easy to lift the powerhead again as all was freshly put back. It didn't work so good the second time as now I have a exhaust leak and wont run with the cover on but hoping the new gasket will solve that. First time (before I pulled the powerhead again) it ran great! Just thought I would leave a follow up. Thanks, Jim

Nice work.

Applause to Jim and Pappy cuz they know 'bout everythang.

All done and runs great.