The two men, according to Tooele County Sheriff's Deputy Keith Borders, were working inside the boat's engine compartment when the fire occurred.
Borders said gas fumes had built up and when one of them made a spark with a wire, it caused a big fire ball.
One man, from Tooele, suffered second and third degree burns, mainly on his arms, hands, and face. He was flown to University Hospital. The other man on the boat was treated at the scene for minor burns.