Agree tough to believe in coincidences. One possibility is the dist cap got smacked and has a crack causing it to intermittently short out so not running on all 8, or an ign wire got damaged. When at the boat and idling, run your hand around the dist and along the plug wires. Get a tingle or shock > there is the issue. If none, suggest replacing all anyway incl. plugs. And take note of condition of plugs and which hole. Post pics.