RedactedNarrative: On 8/23/14, I Game Warden was on water patrol at Lake Mead National Recreation Area. At approximately 12:50 hours,  was fueling at the Las Vegas Boat Harbor gas dock. Once finished the operator attempted to start the vessel. At 12:55 hours Operator briefly started the vessel before an explosion took place under the engine cover. Witness was standing next to the vessel during the explosion. Witness reacted by using a gas dock fire extinguisher to suppress the small flame. The engine cover and internal materials were blown up and out from the vessel. Operator was removed from the vessel and refused treatment from EMS. Once the scene was safe Operator stated in an interview that he had just recently purchased the vessel and had no idea of any modifications done to the vessel. Further inspection of the control panel revealed that the blower switch was in the off position. Operator stated that he did not remember turning on the blower after fueling. At 13:00 hours I arrived to conduct the investigation. On 9/10/13 a further inspection of the vessel engine showed that the alternator was marine grade and fully cased. The damage in the engine compartment was to the ventilation tubing that had melted along with singed wiring and hardened tubes from the high temperatures of the fire. The examination of the interior of the vessel showed fiberglass cracks toward the stern and a fractured wood frame on the floor. The cabin suffered damage to the cabinets and fiberglass. The exterior of the vessel shows that the pressure from the explosion caused the upper shell to lift off the bottom shell causing a full separation. The owner stated that the insurance company inspected the vessel and concluded that the vessel was a total loss ($10,500.00). From the evidence viewed the reason for the explosion was from fuel fumes and the fact that the blower had not been activated before starting the engine. Please see attachments for further detail.