Gi514,
Thank you for the inquiry.
The GP1870F can display any/all information that is contained on the C-Map 4D card. If you're displaying the vector chart (the 4D also has a raster chart overlay) I would ensure that you have set the machine to display all of the available data.
Try this; Menu---Map---Map Configuration---Display Mode---Full.
Additionally it is possible that the C-Map data may/may not contain the 3nm state/federal line. The 4D card we are utilizing (NA-D022 18-Sept-2012 East Coast & Bahamas) does clearly depict the 3nm line in many range scales. If your 4D card does not you may need to inquire to C-Map if they can verify that the current version of the card contains and depicts the data for the 3nm state/federal demarcation line. They can be reached at 800-424-2627 or lightmarine.c-map.com