Hi, I've tried again but the 440S still does not load the map from the SD card (map is unlocked and copied into a "Garmin" directory inside de card). I know now it is unlocked for sure because I manage to see many marine features in my Nuvi 255 when I copied into a microSD card, and then turn off the default map of the unit (City Navigator NT 2011.3). So it seems to me as the 440S is not reading the SD card at all when it boots. I just downloaded the unit's user manual to check if by any chance there might be some setting or feature that could in any way affect the SD card reading, although it is my understanding that one really only needs to plug in the card with the map and it should load on boot up. I even opened up the 440S to check the connections between the SD slot and the main board, which is a small flex multi-connector and visually seems to be ok. If any one has had any experience with this particular unit and Sd cards, please let me know if I might be doing something wrong. Thanks.