Out of nowhere my transducer stops reading at speeds over 30 mph. It used to read just perfect at speeds over 60 but now when I get up to about 25 it freezes up. The speed is the only thing that will work right. The depth gets stuck at 2 ft and it won't give a reading at all of the bottom contour. Any suggestions?

I would guess that transducer is going bad, the signals may be getting weak.  It works both as a reciever and transmitter so if you are still getting readings at slower speeds that is what I would check first.  If it were in the main unit it seems like it would effect it at all speeds.  On mine the speed is read from a seperate scensor possibly even mechanical.

Either what Muddpuppy said or your transducer may be working loose, if it isn't in direct contact with the bottom of the boat it won't read correctly.

If you have a transom mount it may have loosened and be tilted to the back. When the signal gets back to the transom you are long gone. I has happened to me!