we have a 2006 42 fountain with 525's . Recently bought this boat with under 100 hours. Suddenly noticed that one tube of each header has turned a bright gold color, but only on what seem's to be the number 2 cylinder. We got wind of some sort of factory letter knowing of some sort of problem. Does anyone have more info. Thanks

Your header has air in it and needs a restrictor and or Merc water dump balance valve. I have used something like Merc 22-98477A2 at the tails of the exhaust.