I recently purchased a 96 crownline with 4.3 v6, I ran it a couple days after I bought it and it ran fine. About a week later carried my family out and ran it for about a hour, stopped for about an hour and then it cranked up and we ran down river for another hour. The boat started acting sluggish, it backfired and then died. It would not crank after that. Replaced fuel filter, checked firing and made sure fuel was getting to the carb. Any suggestions would be appreciated.