Probably the main circuit board, the same thing happened to mine. What happens is there is a thin plastic waterproof layer over the circuit board, and over time dirt and sand gets in there and wears away at the protective plastic layer, and then when it gets wet, it shorts out and you lose your steering. It happened in a tournament to me and I had to manually steer mine with my hand. I got the board replaced at Rockey's tackle services in orillia, one of the only minn kota parts guys around. It was under a $100 so it wasn't too bad.