My unit will not power on. When I push the power button, the screen changes to a dark black (maybe back light starting), when I release the power button the unit turns off and does not boot. The screen appears to wash or wipe away. I have a 345c unit in the front of the boat, if I move it to the console connections, where the 598 is connected, it works fine. The 598 does the same thing in either location. Any thoughts on the the best way to take care of this is.