Pete,

Welcome to our newsgroup. As you will find out, some of the guys know an
awful lot about technical electronics and will help you get info about many
different options for your set up.

I have a set up like yours and I got a Brookhouse multiplexer which takes
all the NMEA data and streams it to the computer and to all of the gear
including the Simrad auto pilot. I made my system so that all parts work
independently by themselves and then talk to each other when the multiplexer
is turned on.

Check it out at Brookhouse NMEA Multiplexer with optional Seatalk-NMEA
bridge + USB.

Cheers

Ansley Sawyer
SV Pacem