Pull off the covers, unplug the control board and try putting 12v to the steering motor and the lower unit separately (and of course look for burned connections while you're in there). There ain't much to it once you get the 2 side covers and front cover off. It's either the control board or one of the motors, you'll find out by putting power to 'em. If both motors run independently it's the control board. Control board is a simple and fairly inexpensive fix. Either of the motors will be more involved and costly. I think Brenardo has figured out the rebuild process, shoot him a pm he might be able to shed more light.