I just received info from SH concerning using a GX-2150 and a Humminbird 1198ci display, here is the reply from their tech.
Unfortunately I donít have information on Humminbirds products. If you have a wiring
diagram from them we can probably lead you in the right direction.
Donít let the different colors of the wires confuse you. No manufacturer has designed their product to match everyone else's wire colors. What you want to pay attention to is the description of the functions on the wires. Match their Data Out or TX Out with our NMEA
In; or their Data In/RX In to our NMEA
If your plotter can send and receive high speed data (38400 baud) then follow these instructions below.
In the General Setup for the radio, set your NMEA Data In/Out to 38400.
The 2150 will need to receive GPS
data on the Blue wire. This is an input to the radio. Connecto to output of your plotter
The Green, and Brown wires should be attached to TX (-), RX (-) and or ground. Try connecting it to the ground on your plotter.
The output of AIS and DSC
data will occur on the Gray wire at 38400 speed. Output leaving the radio.