GPS, auto pilot wireing questions

[J.D.]

Gentlemen, I’m having trouble connecting NMEA wiring between 3 devices and getting them to work together. I’ve received help from the wiring wizards on this forum before, so I’m sure some one can set me straight this time…. Thanks in advance.

Sending GPS data from: Humminbird 785c Chart Plotter.

Red to batt. +

Black to batt -

Data wires: black, white, red

Sending data from the Humminbird GPS to:

Furuno FCV 625 echo sounder

Red to batt. +

Black to batt -

Data wires: yellow, green, black, white, blue, orange, brown.

Sending data from the Humminbird GPS to:

Raymarine Sportpilot Plus autopilot.

Brown to batt +

Blue to batt. –

Data wires: red, black, yellow, and “screen�? ( I think they mean the shield around the wires ? )

My biggest confusion is how to connect the ground wires. I am not sure about connecting any of the data ground wires together, or to the negative side of the battery. I believe I understand the “data out / transmit “ and “data in / receive “ part of the equation.

I’m hoping some one would take the time to give me wire by wire connection help and a better understanding of the necessary ground connections.

Thank You very much

Jim S.