What is the most appropriate autopilot to control a 30hp outboard used for trolling?

[pkell]

I have a 25' cruiser that is used for trolling on the Great Lakes. I estimate it weighs somewhere around 7000 - 8000lbs. It has an I/O with a V8 that outputs about 250hp to a Mercruiser 888 sterndrive that is mechanically steered. I use a Mercury 30hp outboard with mechanical steering for trolling in the 2 - 3mph range. I want to outfit my boat with autopilot to be used while trolling. The autopilot does not need to be used to control the I/O sterndrive.

I am looking for opinions as to what are the most appropriate and cost effective routes I can take to achieve my goal of trolling along a constant heading, following trolling patterns (do these come predefined or would I need to define them myself?), and navigating to waypoints I have marked with my Raymarine a78 MFD. All of this would be done with my 30hp outboard.

I have previously received the opinion that a great route would be to install a Raymarine EV-200 system pack and use an Octopus drive (type R, I believe) from Aero Marine. This is indeed a great option, but I fear it may be overkill. Could I not get by with a Raymarine EV-200 Sport? Are they still available? I had read an article about Raymarine discontinuing them, I think(?). Do they have any operational or longevity issues? Does anyone know if this would be a less expensive and easier to install option than the T70156 EV-200 system pack with an Octopus type R drive?