Summary: Living in Hawaii I was happy to see the Garman 521s had base maps for my Island. I read the book first and was surprised to find that it was mostly about the additional G2 SD card[$275.00]. Well guess what,the so called base map is useless as a chartploter. You need the SD card to make it work as advertised. So add an extra $250. to the total.
Summary: I ordered this unit because the advertising says it has Alaska and Hawaii base map. The map is so pixellated that it is truly useless! I have to order a bluechart card for it, to make it even functional.
521s with latest software Won't Read SD Cards larger than 2GB
Marina Owner, Amazon
23 March 2013
Summary: First off let me say that until my experience with this 521s Garmin, I have been a loyal Garmin advocate. That has now changed thanks to my August through September 2014 experience with this Garmin unit and the Garmin factory technical support. A neighbor and marina customer of mine bought this Garmin 521s awhile ago at the same time that he bought his new boat motor and trailer.