My fish finder/depth finder is having trouble reading depths at speed. once on plane, it will continue to give a speed reading, but the depth reading will either dissapear or jump up to an extremely high number (198ft.) when I know that I am only in 14 -20 ft. Also, if i do have to cross shallow areas, it will cut out at about 4 ft. I have tried a few things, but nothing is helping. Any suggestions?