Black spot on Plotter

[FirstLife]

I have a Raymarine C90W chart plotter. On a hot day with direct sunlight, it developed a large black spot on the screen. What is it? And can it be removed?

[Dsanduril]

Does the black spot look a lot like this?


If so it is most likely a sunburned polarizing filter on the front of the display. It could be in the display itself, but most (?) of the time it is a plastic polarizing film bonded to the display. If you want to go that far you can disassemble the whole thing, peel off the film, and apply a new one. Then put it back together trying to make sure it is sealed against water. You can get the polarizing film sheet (self adhesive) on Amazon and watch a generic YouTube on the replacement.