1995 C115 Yamaha Started up in morning, Ran about 5 miles and fished for about 5 minutes and went to start up again but it didn't fire. It cranked OK but didn't start, checked primer and was OK. Started back with the trolling motor occasionally trying to start the big motor when after about 1/2 hour it started. It ran fine and has started perfectly since. I dont like the idea that it could happed again and strand me. Any ideas ?