I just replaced a 535. It was doing funny stuff that no one could explain away. I found that the hot wire was pinched between the plywood on the front deck and an aluminum frame member. It worked OK when at slow speeds or while fishing. But, on plane, I lost the screen and had to turn the unit completely off then back on to see the screen. I found where the pinced wire had started arcing after time.
DP
I am a heterosexual male. 2 Chronicles 7:14
"If my people who are called by My name will humble themselves and pray and seek My face and turn from their wicked ways, then I will hear from Heaven and will forgive their sin and heal their land."