Got this hooked up today. Great combo, Standard Horizon VHF/AIS with the little Garmin 740. Couple things that were a little confusing in getting the wiring
and settings right.
ground (green) from the AIS
has to be connected to the ground from the plotter.
output from the plotter (blue) connects to the nmea input on the AIS
The nmea output from the AIS (grey) connects to port 1 of the plotter (brown).
The AIS output from the AIS goes to port 2 input on the plotter (violet).
In the systems/communication menu on the plotter port one has to be set to nmea standard and port 2 to nmea high speed.
Probably simple to others but took me half the afternoon to get it working. Now that it is working it is indeed a thing of beauty.