SIMRAD have published an PDF copy of their "Autopilot Buyers Guide" (sic). It can be downloaded from:
http://www.simrad-yachting.com/Root/Simrad-Documents/Simrad-Autopilot-Guide_en-us.pdf
For use on outboard engine boats up to 35-feet with hydraulic steering, Simrad recommends these core components:
--AC12 autopilot computer, which contains the steering computer and electronics for the drive unit motor and clutch while also acting as an interface to other system components; with low current interface and Virtual Rudder Feedback (VRF);
--RC42 rate compass featuring an integrated turn sensor and NMEA-2000 interface; and,
--RPU80US reversible pump unit that provides the ideal response time of 10 to 13 seconds for a typical hydraulic cylinder of 8 to 10-cubic-inches to move full-port to full-starboard.
The user can then select various options for controlling the system, either with a dedicated controller or a Simrad chart plotter. The most typical choice will be the Simrad AP24 4-inch autopilot display.
The above components are bundled and sold as the AP2403 VRF Autopilot Package with an MSRP of $2,499.