RedactedNarrative: Operator stated boat took about 8 to 10 minutes to start. He smelled gas and thought it was flooded. He let it sit for 5 minutes and turned blower motor on. After that the motor started and when he put boat in reverse, the motor exploded. All occupants exited boat with no injuries. Damage estimate was $7,000 to engine, wiring and upholstery. The motor was a inboard/outboard 350 mercrusier.