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‘72 Johnson 20hp Magneto ?s

T

TreemanMI

New member
Tearing into this non running 20hp I picked up. It had been sitting outside the last several years but “ran before it was parked” :)

cleaned/rebuilt carb. Replaced impeller and lower oil. Tried to start but no spark. Decided I’d tear into the ignition.

Issue #1 - I noticed a decent amount of wobble with the armature plate after removing flywheel. After some research I see there is a fix method to put indents on the brass ring under the plate. Do you put the indents on the top of the rounded surface of the rings? This wobble seems to have caused the flywheel to rub through one of the coil ground wires…

Issue #2 - which coil/points go to the top cylinder? The one near the throttle cam on front side of engine? I marked them before disconnecting and now after doing more online research it appears the previous owner had the plug wires swapped to the wrong cylinders… just want to confirm this.
 
Another question - thermostat. I pulled the cover plate off and there is definitely not a thermostat installed under it. There is a large cylindrical hole that looks like a small tstat would fit in there. And the parts diagram shows one.

anybody know why this motor wouldn’t have one installed if there is a location for it? Just curious why someone would do this
 
1. The coil ground wire probably was not routed correctly. It should be pushed back as close to the coil as possible. No comment on the dinging the brass ring.

2. The coil closest the front (carburetor) is the top one.

3. No thermostat? Simple. somebody removed it. Some people think they know more than the engineers who designed & built the motor.
 
I used to take an old early 80's Johnson 15 to a very salty marine mechanic here in central FL (Atlantic cost). He used to tell me that the thermostats were not needed in warm water environments, and the risk of failure in salt water outweighed the benefits of the quicker warm-up. I think in some respect, he primarily dealt with folks that only maintained their motors when they had issues.

All of my small tillers are freshwater only, so as I work through them, I replace the thermostats with new.
 
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