1966 Johnson FD 20C

Im tryin to get my old motor to run a little better, it runs great hooked up to the H20 hose but when it goes in the lake it seems like it doesnt rev up to full RPM. Any suggestions?

Re: 1966 Johnson FD 20C

It sounds like you're running on one cylinder. Check your spark with a spark testor and then I would remove the inspection plate (if it has one) from the top of the flywheel and see the condition of your coils. If the insulation on the coils are cracked, then they need to be replaced.

Re: 1966 Johnson FD 20C

You can almost bet the farm that it is running on one cylinder. Check the ignition. And don't forget easy stuff first, like spark plugs.

Re: 1966 Johnson FD 20C

I just tuned up my FD-20C with new points, condensers,coils and cleaned carb. Now it runs really good. I read alot of the posts here and found lots of good advise on this motor. One thing that stands out is the spark gap test, if the spark won't jump 3/8'' that cylinder will not fire. I had spark on both plugs but it wasn't untill I bought a spark gap tester then I found spark was weak on one cylinder. One more thing I bought four new coils and one failed after two pulls on recoil, and wouldn't you know it I installed it on the same cylinder that was weak in the first place. After fixing spark issues I ran in a tank to set carb but I thought it should run better and remember reading about the link sink here, and noticed the timing cam had a grove wore into it,so I had to adjust very little. Now it runs very good. good luck.

Re: 1966 Johnson FD 20C

Right on. Good to hear. You'll enjoy that old motor. They're one of my favorites.