RedactedNarrative: Operator advised he just purchased V1 on 3/17/18 and he was not aware of any work being done on V1 prior to his purchase.  He further advised he had filled V1 with approx. 80 gallons of fuel on his way to Beaver Lake. They launched V1 and went out a little ways to swim while his wife parked the vehicle. He said after a short swim, all occupants re-boarded V1 and he started the engine to go pick up his wife from the shore.  When he turned the ignition, he immediately heard a "pop" and the motor cover blew off. He was able to flag down another boater who helped get everyone off V1 safely.  V1 continued to burn for approx. 30 minutes.  Operator stated he did "vent" the vapor/gas after fueling but admitted he should have probably vented again after he launched and tried to start V1.