Just purchased a 997 Humminbird but the problem I have is the plotter is useless where I fish. I had a garmn unit before and downloaded the Mapsource topo map and had a map of everything. Humminbird only uses Navionics charts and they don't offer a map of my fishing area. Any of you gurus (sp) know if there is a way to make the 997 accept the Mapsource?