[gsharapa]

I've been down this road many times with big cam motors in Offshore boats and Cobras. If you have a big cam you have very little vaccume which is allowing the power valves to open and give your engine too much fuel. You were right on your assumption that going to 8.5 was the wrong direction. In the Fountain offshore boats I was running 2.5 and in my Cobra's with big cams 3.0 to 3.5. Drop the power valve from 6.5 to 5.0 and see if that makes a difference and down from there. They are cheap and easy to replace....good luck.