Navman Fish 4150sx GPS Receiver "depth finder reads wrong" Questions

depth finder problem when i reach speed of 10-20 mph the depth indicator goes haywire and give depth ranges of 350 to 700 feet in water that is some where in the range of 5 to 20 ft. once you stop or ...

...depth i certain areas; but only grey colour. What are we doing wrong? The image on my fish finder has a ghost like worm going across the screen. It doesn't read structure at all but will give you the ...

...depth finder along with the Navman GPS unit when I purchased my Bayliner Trophy 20Ft. Offshore model. Everything was ok for one year and it has been downhill since then. Losing signal, unbelievable ...