After looking at the Solarcraft 18 Pontoon Boat the other day, I got to researching what they were using for a joystick controller. That led me to finding Lenco Marine and their JoyRide setup. Two small trolling style motors mounted on powered trim-tabs.
They don’t turn, and there is no rudder. Apparently just use differential power for control. For a smaller boat, this is a slick setup. The web site has lots of downloadable brochures and the like.