You can't upload on mine either. You still have to enter stuff manually when you get back to the boat.
This is supposed to be possible using a "user chip", but I know Mike Garside has been round this loop a few times with the manufacturers, but still cant get it to work yet.
Meanwhile, however, I get great fun out of doing all my route planning at home on the PC.
See
http://www.biboa.com/cruising.htm for some detailed examples of my handywork.
As you can see this sort of thing is particularly useful if you wish to share routing information with others.