Something with the big motor. The most info I heard about it was him talking about it at weigh-in. He said, "I don't know if it was bad fuel or what..." which I thought was a funny way to not give bad press for Mercury. He's sponsored by Mercury, the same brand of motor that broke down Jordan Lee last year in the Classic.
Why would you want to give bad press to the companies paying your bills??
Even if it was something that failed on the motor, that stuff happens. It is a machine with lots of moving parts with a long track record of reliability. But mechanical things fail occasionally.