RedactedNarrative: V1 HAD JUST BEEN FUELED UP BY BRADY MT MARINA.  OPERATOR ATTEMPTED TO START V1 AND AFTER 12 MINUTES OF ATTEMPTING TO START V1, THE OPERATOR WENT TO THE BACK OF V1 TO CHECK THE MOTORS. THE OPERATOR NOTICED FUEL IN THE BOTTOM OF THE HULL AND TURNED TO GO BACK TO THE FRONT OF V1; AT THAT TIME THE FUEL IGNITED AND A FLASH FIRE CAUSED SERIOUS BURNS TO THE OPERATOR.  UPON INVESTIGATION IT WAS REVEALED THAT THE MARINA NOTIFIED THE OPERATOR MONTHS AGO REGARDING LEAKING FUEL IN V1. A COMPANY WAS HIRED BY THE OPERATOR TO REPLACE THE LEAKING FUEL TANK RECENTLY AND IN DOING SO ALSO FAILED TO CONNECT THE VENTILATION HOSE BACK TO THE PETCOCK. THEREFORE, WHILE FUELING GAS WAS SPILLING FROM THE PETCOCK TO THE HULL OF V1. HOWEVER; DUE TO OPERATOR'S INJURIES/MEMORY WE ARE UNABLE TO DETERMINE THE EXACT IGNITION SOURCE.