RedactedNarrative: Operator stated that he and his family launched their vessel at wind creek state park. He said they rode from the ramp to dennis creek and then toward bay pine marina. Operator said that he heard a back fire and the engine cowling blew off and flames began coming from the engine compartment. Passenger retrieved a fire extinguisher but a passing boater advised them to jump overboard and abandon the vessel due to the severity of the fire. The operator and passengers were then picked up and transported to bay pine marina by the boater. Operator advised that they had been riding only about 15 minutes prior to the explosion and operator had just picked up boat from kowaliga marina from being worked on.