Unfortunately, most of the yachting autopilots are set up to
work with reversing motors, so you will be paying for a lot of unnecessary circuitry for powering motors with variable speeds when all you need is some solenoid outputs. Look at Comnav, WH, and Coursemaster. Some companies market their autopilots based on boat length, but you don't need any more than a basic
small boat system--its harder to keep a
small boat on course than a big one, and you don't need any extra
power to control your
rudder. A rate
compass will provide better control in rough seas.