Mate have you checked the lowrance web site to see if you are running the latest software i beleive they bought out new software that had something to do with G.P.S problems its easy enough to do just buy the smallest sd card plug into your computer download the program then put it in the g.p.s sd holder turn it on and away it goes i did it to my lcx15 about 2yrs ago worked great go to there site and have a look bluefin59......