My motor has an intermittent problem. Sometimes it will start and run fine. Some times it won't hit a lick. No fire to all 6 cylinders. Was checking for spark and it started. Next day, won't hit a lick.
check the wires going under the flywheel, I had a boat that did the same exact thing , turned out to be the wires were rubbing the bottom of the flywheel and had the coating wore off them. I guess they were sometimes touching and it would not start. anyway taped them up and never had anymore problems..