Some thoughts
1. It must be compatible with your boat's steering system, so for a Cat36 that means a wheel steering mechanism. 2. It must have sufficient drive power & response time for the type, size, and displacement of your boat. Suggest talking to manufacturers of autopilots to see what they recommend in their product lines. Check with a Catalina Dealer to see what system the factory installs on Cat36's. Also, check in with the Catalina 36 International Association to get owner feedback. 3. If you intend to integrate the autopilot with other on-board instruments and navigation systems (which is REALLY nice when it works!), I'd suggest starting with the manufacturer of those instruments. Catalina factory installations tend to be Raymarine/Autohelm products, and they integrate very well (have them on my Cat320). Mixing products from different manufacturers can work well, but you could encounter some tricky integration and compatibility problems. Also, product warranties between manufacturers might be an issue to consider. 4. Check your pedestal, steering mechanism below, and rudder bearing for adjustment, excess play, wear, etc. A sloppy steering system can really make an autopilot work harder & increase the power drain. If your steering is sloppy, you might need to include a rudder position indicator option (more$$; it provides an additional control loop to improve response); if there really isn't any play in the wheel-to-rudder response, I wouldn't bother. 5. Consider where you can place the fluxgate (electronic) compass that is used for steering. It needs to be close to your boat centerline, but reasonably far away from magnetic materials (e.g., a steel engine block), yet you'll need to route the cabling up to the pedestal-mounted control head. 6. A factor in your selection is the ease of calibration. Once installed, you need to swing the fluxgate compass to calibrate its local deviation, and then enter offsets to match the displayed heading with your binnacle compass. The Raymarine/Autohelm ST4000 system is very slick in that regard -- don't know about other brands. 7. Almost every system today allows a few "response" settings. You may have to experiment a bit for your boat & its trim, but generally the standard settings are pretty good unless to bought an under- or over-sized system. Most people say buying slightly oversized is better -- perhaps, if your boat specs are at the edge of a model's performance limit. 8. Reliability of any complex electronic system on a boat can be an issue. If you plan extensive cruising away from support bases, go with a vane steering system. 9. Finally, no matter what system you go with, practice proper sail trim. If the boat is trimmed such that you can let go of the wheel without it going immediately off course, then the autopilot can work so much easier with less power drain. If you have to fight the wheel, so will the electronics!
