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1973 Johnson 20hp conversion to under flywheel coils.

D

Daveparm

Member
Hey all,

I just picked up a new project, a 1973 johnson 20 with no spark. It is one of the designs Johnson touted as having quicker spark (slow by modern standards) , by using a trigger coil to fire the two ignition coils located closer to the plugs. My other 3, 22ci 18's and 1976 25 use the standard under the flywheel approach. I haven't popped the flywheel, but was wondering if I could convert. I boat in open waters and like the redundancy this older style offers as the points don't rely on each other for the system to work. I always stock spare ignition wire and have quite a few donor mags I could use parts from.

Is this possible? Any drawbacks?

Thanks.
 
I believe it is possible on the 22 ci motors, but don't know the exact details. Specifically, not sure about the flywheel. The Lo-Tension ones have two sets of magnets. while the Universal Mag only has one set. The extra set may not be a problem, I dunno. The points' breaker cams are different but just slide off & on.
 
Yes, the flywheel was one of my concerns. I was assuming the cams were the same, thanks for checking that! Do you think the extra magnet would over charge the coils with the extra pass? I suppose iI could find another flywheel from eBay, Joe, exec.
 
Popped the flywheel & I did a little digging. Looks like the same cams were used on the later pre 76 25hp 22ci. With the under the flywheel mag. I plan to use the existing can. I think it should work
 
73-76 Lo-Tension mag uses 318488 cam. 1971 and older Universal mag (what you are planning to convert to) uses 316583 cam.
 
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