Hi Floyd, i agree with Mark, GT-31 is "the one" for speed sailing and the only one fully accepted in GPS Speed Surfing championships, it has the last generation chip Sirf III and is the only one that you can insert a 2Gb memory card and save months of sailing data and use it own memory as a back up. You can take a look at the manual at
http://www.freight-focus.com/download/gt31_manual.pdf
Rgds.
willy