I've had my Garmin 498C linked to my Humminbird 931C and also my 778C. Both my Humminbird units are fishfinder only as I hate spliting screens, tough enough to see the whole screen, let alone half of it. I linked them up to get the speed on the Humminbird screen, and also I can mark a brush pile on the fishfinder screen and use it to bring me back. I use the Humminbird waypoint, cursor position, option to bring me in. It shows course to steer and feet to waypoint. I can just watch the fishfinder screen looking for the brush pile, with my AP bringing me in.