Steve,
I have a SailComp 103AC, I've connected both NMEA input and output, and I'd be happy to chat about it. (In fact, I just re-wired it yesterday! I was sick of not seeing the masthead readout at night due to really wimpy backlighting, so I moved it to the cockpit.) Of course I know nothing about the Standard Horizon GPS. ;-)
Ryan Pierce, #337