Humminbird charts are blacked out

Have a problem! My neighbor bought this boat and came with an humminbird ion 12", worked perfect when he got it, now you can not load any chart(sonar, side, imaging, nor down imaging) map did work but now it's blurry. Also when I crank motor my temperature will go from reading right to 40 degree wrong! Don't know much about this unit just trying to help him out, any help is appreciated!

They require a lot of power, any corrosion, less than optimum circuit size, and battery condition will affect it.

Check the power to the box that the transducers are connected to also.