Have the humminbird helix 10 mega, but the builtin charts are terrible for Lake Marion. The LakeMaster HD only includes Lake Moultrie and not Marion which is just crazy to me. Any one here running the humminbird units and have a good recommendation for a good chart software for Lake Marion to show general contour lines and other route info? Is the Navionics + a good base starting point? We have learned a bunch by idling around and following others that "seem" to know what they are doing as far as navigating the lake, but would love to have some view of things before even heading out. Maybe I should have went with Lowrance but too late now.