I just replacd my x 510c with a HDS7.If I tell you I was pleased, I would be lying. I have been trying to set it up and have only been out today, water was muddy. Spent time on the new unit. Forgot manual , left at home, I was lost. I could not get GPS to track my route. There is nothing wrong with the unit. Only my feeble mind trying to set it up.I feel the manual could be more helpful and more self explanatory. If I knew how to use this sonar/ gps I could write a better user manual, too many things not explaned. For instance there is a blinking exclamination box in the lower left corner that I have no idea what it is telling me. I am not giving up..... YET , takes us "OLD GUYS a while to catch on. This thing will do things I never thought of.Any one wishing to offer any tips, I would be thankful.