coming down the canal after a cruse one engine went out no spark . checked key switch and all fuses ANY Ideas !

Check the grounds at the rear of engine both sides. Same thing happened to me fuel pumps turned on motor turned over just no spark. Mine was loose on port side. Good luck.

Probably a stupid question, but did you jiggle the shifter to make sure it was in true neutral? Safety switch is connected? Jiggle the main wire harness? No BS, Mercury has a wiggle test they do when they plug the computer in and jiggle all the wires.