Steve, you're right about the Seatalk cable connecting with the autopilot. Part of my "confusion" is that the NMEA connector has NMEA183 data but so does the Seatalk connector. Another case of standard data using Raymarine's proprietary connectors.
I ran all four Raymarine NMEA wires from the cable connected to the NMEA output behind the C80 to a connection strip behind the helm and that's where the connection to the VHF was made, rather than use those telephone snap on connectors provided by Raymarine. That way, should I get any other NMEA183 device, it will be easy to connect. I intended to use it for a Navman connection as well but went to a Seatalk2/NMEA2000 fuel flow system instead.
I ran all four Raymarine NMEA wires from the cable connected to the NMEA output behind the C80 to a connection strip behind the helm and that's where the connection to the VHF was made, rather than use those telephone snap on connectors provided by Raymarine. That way, should I get any other NMEA183 device, it will be easy to connect. I intended to use it for a Navman connection as well but went to a Seatalk2/NMEA2000 fuel flow system instead.