Lowrance gen2 touch 9 on console 7 up front. The front graph will not read the navionics from the back graph at the lake but when I get home and turn them on it pulls up the map just fine. Anyone have any thoughts on this?

Your ethernet cable may need to be replaced. That is the first and easiest way to troubleshoot your problem. You can plug them in the back of the unit externally without having to fish or run cables throughout the interior of your boat to see if that fixes the issue. One of the biggest issues with ethernet cables is people cinch them down too tight with zipties essentially breaking or weakening the components on the inside. This problem is way more common than people realize.

PRO TIP: When I rig my boat for the first time, I will run 2-3 ethernet cables on that initial rigging and label each end of them color coded with a Sharpie or taped with 1,2,3 or A,B,C so you can tell which cable ends go together. It is way easier to do this at first than to have to go through and deal with it during a tournament or later on in the year.

I had the same problem on my last boat. Sometimes the maps would show on the bow, sometimes they wouldn't. Borrowed an extra ethernet cable a buddy had and hooked it up, as Clark said, externally and that was the issue. I had it cinched down too tight with zip ties.