[Marine-58]

This may be the dumbest post of the year and certainly do not intend to insult your intelligence, but did you verify the firing order for the plug wires going on the distributor?

1-8-4-3-6-5-7-2

Driver side 1-3-5-7 Passenger side 2-4-6-8

Are you sure that when you stabbed the distributor that it isn't 180 out?

Have you tried another carb?

When I get lost in a nonsensical trouble, going back to the very basic beginning usually helps. Interesting trouble, looking forward to seeing what the fix is.