1975 evinrude 3 cyl 70hp spark issues

i had my boat out the lake the other day and wen put in gear it would idle along nicly once i added revs it stalls so took it home suspecting feul issues but before i decided to clean carbs and rekit them and what not i decided to check spark with a timeing light found good flash and spark on the bottom cylinder closest to the prop then checked the next cylinder up and had minor spark and very irregular then tryed the same on the top cylinder closest to the flywheel and nothing at all but playing round it wont start less the bottom lead is pluged in so got it running then disconnected the cylinder with good spark and it still seem to run fine??? this confuses me could someone explain how??? next i swaped the top coil with the bottom one (the coil that had no spark with the one that had good spark) and once again had good spark on the bottom cylinder and none on the top and no change in the middle could this be a power pack problem or is there more i can do as far as process of elimination

The powerpack is suspect.----But first do an ohms check on the stator charge coils and the trigger coils.

thanks will try this in the morning