Scott,
You can but you need to use your computer to do it ;
- You will need to merge the .usr (lowrance file on the first page of this thread), and your existing .usr file which stores all you gps marks.
- GPSU is a software tool able to merge the 2 files,
- copy the new file back to your data card and reload your gps marks into your unit.
Regards
HOnda.