Incidentally, you can download the IOS or Android app called
Navionics Boating for a free trial. After 30 days or so, it costs $10 or $15.00 a year. It has ALL of the data that is on the expensive Navionics card, only it is on your phone or your pad.
You do NOT need Web access or Data access to use it on your boat. It runs off of the GPS signals, not towers.
I find the phone to be hard to read in the sunlight. I might buy or make some sort of shroud to shade the screen so I could use it more on the boat.
However, if you like it and use it, you can always step up to the card that goes in your FF (assuming your FF is compatible). That screen would be far more readable.