1974 Johnson 15 hp missing

[Czar]

My 1974 Johnson 15 is missing and backfiring. I have replaced the points and condensers and the plugs. It runs not too bad when not under load but as soon as you try to take off it will either die or really stumble. Sometimes it won't get past idle speed at full throttle, just stumbling along. Any ideas ? Would a bad coil cause this? It has spark in both cylinders or so it appears. Is there a way to set the timing on this engine? I set the points to .020 on the set mark.

 

[hondon]

Re: 1974 Johnson 15 hp missing

How did that flywheel key look when you had the flywheel off?.Did you just change the points and etc. as regular maint. or was this problem there before?Compression still good?

 

[seahorse5]

Re: 1974 Johnson 15 hp missing

Assuming that compression is good and that the fuel system, linkage, and carb is functioning properly, the driver coil, under the flywheel connected to both sets of points, was a weak spot back in '74. There was a service bulletin about it back then. It is only around $25 and is easily replaced. The only test is an ohm reading, but that can be OK and the coil still would affect the ignition system.

 

[Czar]

Re: 1974 Johnson 15 hp missing

Thanks for the help, yes the key looked ok and I was changing the points due to the problem not regular maintenance. I suspected the primary coil under the flywheel and was hoping someone else thought the same thing. <br /><br />Thanks