Employees were inside a building, replacing the fuel filler hose on a boat. The fuel filler hose runs down the port side of the boat and under the deck to the fuel tank which is mounted in the center of the hull. The employees used an electric heat gun to soften the thick rubber hose to allow for installation. A flash fire occurred in the gasoline fuel tank on the boat. An employee sustained first-degree burns to the face and second-degree burns to both hands. The employee was hospitalized.