A mechanic believes it was a mechanical issue that was triggered when the gas tank was filled up. A boat on the water in Harrison Township exploded, injuring four people. Big picture view:Meanwhile, the owner of the boat came back to the marina trying to figure out how it happened. He tells FOX 2 that the mechanic believes it was a mechanical issue that was triggered when the gas tank was filled up. Dig deeper:The incident shook the Harrison Township area, with Macomb County officials responding to Tow Boat USA on South River Road after the boat exploded Thursday afternoon.