Late comer to the tread... Tim it does sound like like a bad coil. Had the same issue with my boat. It would run for an hour or so then loose power and stop. Wait 10-15 minutes and it would fire right up and run for another hour. Ran the gambit of troubleshooting for about a month.
Finally gave up and called the Island marine mechanic and explained the symptoms. He called me back about 20 minutes later and said "it's fixed". Just a bad coil as he expected. He said it is the most common cause for sudden loss of power. Boat has run great ever since.
