RedactedNarrative: Operator took his father-in-law's boat out to Lake Quinsigamond for a test run for the season.  He gassed up the boat with about 15 gallons prior to driving it to the lake.  He was alone when he launched, ran, started the boat and ran it around for a few minutes until his wife arrived with his daughter.  
  
  He ran the boat around the lake for about 30 more minutes with his daughter when he turned the blower off.  The engine continued running and about 5 minutes after he turned the blower off there was an explosion and the boat was on fire.