Engine quits after it runs for 30-40 mins

Hi All,
I have an 86 2001 and it runs great, however ever since I pulled it out of storage I have ran it twice. Both times It ran for 30-40 mins and then quit. New gas this year and I winterize boat properly.   It will not start back up until it has sat for a long while. It was converted to electronic ignition by previous owner. Not sure if it's the coil or what it could be. I have owned it for about 4 years and this is the first that it has done this to me. Speed is not a factor either when it just quits running down the river ironically both times have been at idle. Any help would be appreciated. Thanks.

So the coil over heating could be the cause of why it quits? If so, it makes sense that I'm unable to start it until its cool again.