If maps is greyed out it could be one of two things:

1) your GPS unit may need a firmware update (check www.garmin.com support)

2) the basic software doesn't come with that information in it. You have to purchase the marine chart for that region. If you have that marine chart (and can see all the channel markers and navigation aids in Mapsource), you need to unlock your GPS to work with that map set. The marine chart resource CD should have the information about how to unlock your GPS unit. You are allowed two GPS units to unlock with any one of the marine chart regions - their security is pretty tight with those charts (as they make a fortune on them).