We just recently had a garmin 400c depth/fish finder installed on our boat. Not a week later our GPS unit was stolen. now we have replaced it with a Garmin 440. i was thinking that the transducer for the 400 should be compatible so before I wired it I decided to plug in the depth finder cable to the GPS. The GPS worked, but it would not read the depth. I haven't had a chance to mess with it but I figured I would see if anyone had any info for me.