Solved this problem today. The F225 on a bracket severely limits your options for mounting the linear resistor that is part of most outboard autopilot installs.. Things are tight back there. Everywhere you put the thing it binds up on something. You have to watch out for tilt and the thing changes vertical position as you steer lock-to-lock. We ended up making new standoffs from starboard and extending the stainless steel arm that pushes and pulls on the plunger. I'm not a fan of this expensive resistor unit. Seems like high-end outboards should provide a rudder position signal as part of the package just like tilt, RPM, etc.
I look at electronic toys with some skepticism, but autopilot is a "must have" item. For trolling, it allows you to ge back and tend the lines without worrying about the boat going in circles. For general navigation, it must save you money by getting you from point A to point B by the shortest path.
We tried the Raymarine S1000, but it has a major shortcoming in that it uses the GPS to get its heading info. That allowed them to produce a very economical unit. The problem is that if your speed over ground decrease to the point the your GPS can't determine your heading, the autopilot just quits. So if you are trolling into the wind or into a 5 knot current, it gives up and you start drifting aimlessly. Raymarine has made software changes that increases the time that the unit remembers your last heading, but it did not solve the problem. The other flaw seems silly, but it's real... Sometimes you tell the autopilot to do something stupid, like send me on a heading 180 degrees from where I'm going now, and it does what you told it to do and the normal reaction is to punch the STANDBY button. When you do that on the S1000, the wireless remote pops out of its mounting bracket and flies across the pilot house. I said it sounds silly, but it has happened to me and other drivers of my boat numerous times. I think the S1000 has safety issues and have let Raymarine know.
We removed the S1000 and moved up to a unit with compass and rate gyro. Get the right control head and you can steer the boat with a knob. Cool stuff!