1968 Johnson 20hp missing/stumbles

[lakegastonpack1A]

I have a 1968 Johnson 20hp that generally runs ok, but sometimes stumbles and misses on acceleration. Usually, after a couple of minutes, it kicks in, and runs fine. Motor starts good, idles ok, and runs fine once it kicks in. Spark plugs, points, condensers all new. Gas fresh. Any ideas ?
Thanks !

 

[racerone]

Are the coils new ?---------Have you checked the bottom of the coils for burn through?----------Have you checked plug wires for cracks ?

 

[lakegastonpack1A]

The coils are not new, but they look ok. Same for the plug wires. I am messing with it right now--idles fine, but stumbles bad on acceleration, but then it will just kick in, and run ok.
Seems only to do this on acceleration, doesn't miss just riding along.

Thanks.