'64 500 W/Kiekhaefer stalls then will not restart

My engine starts within the first second of turning the key and runs great from 1 minute to an hour then stalls ( only happens when idling)and will not restart(cranks great but will not fire).I've replaced plugs,wires,coil(even though the other still produced good spark),points,and condenser.I've cleaned the distributor cap points and the rotor contacts and still problem persists.If memory serves me correct I'm sure I had it stall when the wiring harness was disconnected while testing out of the water,but my memory is not as good as it used to be,plus frustration makes me forgetfull,so that should rule out bad switch and k/switch.I've tested every plug wire for spark when it does stall and nothing,then I pull the magneto assembly and disassemble and reassemble,reinstall and you guessed it,it fires right up.So what am I missing or overlooking that is causing this?I've ohmed everything as I disassemble the magneto to see if there are faults any where and I'm coming up with nothing and as soon as it is checked thuroughly over and reaasembled then reinstalled it works.I'm loosing hair and valuable leasure time with this and am getting sick of being towed back in(once by a 8ft dory) and even worse when out on Lake Michigan which can be hazardous.Anyone with a slight hint at what could be the problem I'm willing to give many thanks to.

Re: '64 500 W/Kiekhaefer stalls then will not restart

Doesn't anyone have an idea to help me solve this problem.I'm leaning toward a bad cap or rotor causing this gremlin problem,but they just are not readily available to swap out and test,so I could really use any ideas.