Fullsize boat with Ardurover

Yes I am a newbie, first post and excited about this forum. I want to upsize things a bit.
I have 1 1974 Silverline Antigua 18T powerboat. Normally it is powered by a 188 Hp V-8 stern drive but when fishing I use a 7.5 Hp “kicker” outboard. I am assembling a 12V linear actuator for remote steering while fishing. This was to use a Mom SPDT switch on a long cable for port and starboard command inputs from anywhere in the boat.
Then I discovered my Humminbird sonar/GPS has a NMEA output… Hmmmmm
Now I would like to find or build a board that will decode heading corrections based on GPS waypoints to drive a pair of relays to operate the actuator. There is also the possibility of throttle and shift control for later development.
Am I nuts or has it been done, can it be done. I think actually it is fairly simple.
I am 71 years old retired electronics tech, pilot, Ham operator, and tech junkie.
Thanks, look forward to another fun forum…

This article might help you out: http://hackaday.com/2014/01/08/ride-captain-ride-aboard-your-arduino-controlled-autopiloted-sailboat/
TCIII Developer