Humminbird Matrix 17 issue

I actually have a couple of issues.

1) When graphing fish (or maybe they are not fish) I always have the fish ID symbol ON because when it is OFF, I get not markings at all....no arches. It doesn't matter what I have set for sensitivity. However, I do get horizontal black lines that are sometimes in clusters. There are times when there is line after line stacked on top of each other. Would this be fish or is there something wrong with my transducer or is it picking up interference? It seems that I get more confused everytime I go out on whether or not I am marking fish. I have having a very hard time telling the difference between baitfish and actually fish.

2) The inside of the display is fogging up and when it fogs up, it has scratches on the inside of the display. It is very annoying. Anybody else have this problem?

I have the same unit and when I first got it I had the same problem with locating fish. Try these settings and see if it helps. You might have to adjust it even more for your liking.

Sensitivity--19%
Upper range--0
lower range--Auto
Chart speed--5
bottom view--inverse
beam--200/83 khz
fish ID---off
fish ID sensitivity--6
RTS window--wide
RTS zoom width--wide
Surface Clutter--3
noise filter--medium
max depth--auto
water type--fresh
depth lines--on

This is a starting point for you. You will have to be in the advanced user mode for these settings. Hope this helps !!!