1985 75hp Trigger question

[erkllis]

I have recently purchased a 1985 75 hp Merc. Took it out for the first time and couldnt get anything on top end. Found white wire from trigger had deteriated to the point it would crumble to the touch. I assume it had gotten hot at one point. Bottom 2 cylinders were not firing. I need to replace trigger obviously but what could be root cause of failure. Would this have damaged switch as well.

[boats.net]

Mercury's are bad about that, the wires just deteriorate after time.