I have what I believe is a 1982 Merc 50 horse(correction, it's a Mariner if there is any difference?) on a little boat. The engine fires on the top two cylinders, but not the bottom two. It's not something as simple as spark plugs, and/or wires as I've checked that. All four plugs work fine when tested on the good top two cylinders.
Is there any common thing that would cause the boat not to fire on just the lower two cylinders?
Also what is the long plate like thing that everything connects into right on the side of the motor - the coils hook into it, and there are wires coming into it - is it a long CDI or something? Or is it something someone told me is a switch plate? There are I believe 8 wires in one row, and 5 wires in another row (closest to the starter).