Easiest way to determine if it’s a coil is to swap them around. Unplug them from the ampehnol plug and swap them. If the issue follows the coils, you’ll know if it’s a coil. Also, check all coil and pack grounds.

If the coils check out, next best bet would be the power pack.

99% of the time it is the powerpack/CDI unit

Which CDI did you move from which motor? If it is what I’m thinking both boxes need a S.C.R.
I have done Mercury’s but no OMC’s yet. Use potting solvent & see if you can read the factory part number on either SCR as they each have one per cylinder it sounds like.

I’m confused. Yes, it is a little tricky to move those primary leads in the rubber connector, but it can be done. They make, or you could make jumper leads with the pins/sockets so you can swap the leads without pushing the pins out of the rubber connectors.
But then it seems like you go on to say that you DID move the leads, and when you did the opposite cylinder lost spark. This would indicate that both coils sparked when you connected each one to the good primary lead coming from the pack. If I have this right, that usually indicates a bad power pack/CDI unit.
Nonetheless, all of the other components should be checked as well. Marginal components/connections might have caused the powerpack/CDI to fail, you don’t want the new powerpack to prematurely fail as well.