For some time I've wanted to put together the control system needed to control via radio a full-sized boat. I finally got the control system done, and did a very rough test using a pair of electric trolling motors.
http://www.dtbradio.com/rcboat1.mpg is a VERY rough video] of the boat under RC control. I will post more details of the project later, but it is based on a PICAXE 28X2 microcontroller, a pair of high-current relays, and a pair of very high-current bipolar transistors.