It can be changed. 1. main menu (advance user mode) press menu key twice. then select the setup tab. select one of the following menus. depth offset temp. offset or speed calibration. use the right and left cursor keys to adjust the offset. this can be found in the Humminbird manuals found on there website under support manuals it is on page 216 helix 12 chirp mega SI G2N

http://www.humminbird.com/Category/S...oduct-Manuals/