[dgax65]

I think that most of the Garmin 76 line have a NEMA output cable included. That allows you to output to a chartplotter or radio. Humminbird is pushing their own GPS receivers and they don't have much on their website about using non-Humminbird GPS. You could probably splice the NEMA cable from the GPS to a Humminbird GPS input cable. Might not be worth the effort, though. Other brands might be a little more user friendly.
I like having a backup, so I take a handheld Garmin GPS 76 in addition to the hardwired GPS receiver for the Humminbird Matrix 77c. Next thing I need to try is cutting and pasting Lat/Longs from my Humminbird software into my Garmin.