RedactedNarrative: Vessel #1 (V#1) was on Thunderbird Lake at Fisherman's Point. While the operator of V#1 was backing the boat away from the boat trailer he advanced the accelerator into reverse for a little more thrust when the vessel blew the back hatch off the back of the vessel. The operator went for the fire extinguisher and used it until it was empty. The fire was not out so the operator jumped into the lake for his safety and swam to shore. The area of explosion was 312 ft. from Fisherman's Point Parking Lot, 232 ft. from Fisherman's Point Boat Ramp, and 381 ft. from SE Corner of Fishing Pier. The operator advised me during the investigation that he ran the ventilation system for approximately 3 min. before he started the vessel.