I can't begin to answer your question, but I'd be calling humminbird direct and asking them. It's a little bit of a pain having to wait on hold for someone, but generally they are pretty helpful. You might also try messaging Humminbird Greg direct. I had questions and he was good about addressing each one. I'm very interested in what you find out. My plan is to install and 898 on my dash and interlink it with a 788hd di on the bow of my boat. If your having issues with them synching together, I'd sure like to know before I take the plunge.

Maybe someone else will have some better insight on your problems. Good luck.