Digital tach gauge problem

My 1997 digital tach gauge for my 250 hp just started having problems. It does not display all of the black marks. I just installed a new Raymarine C series chart plotter and fish finder. This is the first time I used the boat since I did the install. Could I have done something or did it just wear out.
Thanks.

[boats.net]

Probably not but check all gauge wire connections are connected.