Check spark on all four,
then undo the distributor lugs of and have a look at that,
l have a 1979 70 hp that we fitted a new MSD cd unit to back in feb,
used it a dozen or so times until winter and life got in the way,
would still start it in the yard when able,
Started at home 10 days ago prior to going down to the boat ramp 500yds away,
idled fine for 5 mins at the ramp,
then started to miss and run rough....had a large sneeze then stalled...wouldn't start after that,
took it home...no spark
checked wiring ok
undid dizzy ( preamp type ) rotor came out easily, almost fell out,
Looks like preamp or rotor is the cause, not sure if we will continue with this motor
Very interesting read and videos
and the connection to Frank A