Boat recommendations

After reading lots of references to Pixhawk and autopilot I’ve decided to take the plunge. I have been looking into the different models and options and it’s a bit overwhelming, and you know if I pick one it will be the wrong one. So which unit would be the best for me?

It will be in a boat, to start with to learn the basics it will be a twin prop cabin cruiser, with a rudder, mainly because I have one. Eventually I want to make a twin thrust prop boat that could maintain, loiter I believe it’s called, using twin thrust props would be similar to slid steering in a rover, I think.

Thanks for all comments and suggestions
John