A stainless steel bracket that mounts directly onto the wind vane allows a simple, inexpensive, tiller autopilot to handle a very large boat. The autopilot operates at virtually no-load power consumption to move the airfoil holder that steers the servo rudder, just as if was driven by the wind. Water flow over the servo rudder produces the hydrodynamic power to steer the boat.
Mount the stainless steel autopilot bracket to the turret tube of the wind vane using stainless steel hose clamps. Slide the retaining pin in the back of the autopilot into the hole in the bracket. Wrap tension cord (bungie cord) around body of autopilot and bracket. Put a pin in the end of the autopilot ram and attach a line to it. Attach a block to the turret tube with another hose clamp or other means. Lead the line through this block as shown and to one side of the airfoil holder. Attach a tension cord to the other side of the airfoil holder and to the back end of autopilot. Adjust both line and and tension cord so that when the autopilot ram is halfway out the airfoil stands straight up.
Now set the course on the autopilot and as the boat goes off course the ram will move in or out. As the autopilot ram moves out the line will pull the airfoil to one side, or as the ram moves in and there is slack in the line, the tension cord will pull the airfoil to the other side. This will move the servo pendulum and thereby steer your boat.