2003 Yamaha F60 carb question

[coderunner]

I have been fighting with this motor (F60TLRB) because it has no power under load. Ran fine in the past. Specific question is about my carb #2.

I ran in the water under load with each spark plug disconnected one at a time. There was a noticeable difference when each plug was unplugged except for when cylinder two was unplugged. When cylinder two was unplugged, it ran about the same as when it was plugged in. This leads me to believe that cylinder or carb2 is the problem. I went back and looked at the pic I took of the original spark plugs when I pulled them. Plug 2 was rather black (see pic). Four had a rather brown appearance. Not sure what to make of that. The shop has cleaned carbs twice. Going to pull carbs and clean carb 2 myself soon. Is there an adjustment that will make carb 2 run too rich with high speed / under load? Is this is a high speed / main jet issue? What would make plug 2 so black? I know there is a pilot screw that is supposed to be installed and correct from the factory. Maybe dig into it and check adjustment? I believe it helps adjust how rich the cylinder runs? All plugs have spark with spark tester. Plugs have been replaced.

 

[coderunner]

I checked the pilot screw for each cylinder. # turns out from all the way in:
#1: 1 3/4
#2: 1 3/4
#3: 1 5/6
#4: 2 1/8


I was hoping to find that #2 was dramatically different, but wasn't. The new #2 plug now appears black despite hardly any time running.

 

[99yam40]

#4 is the only one that looks like it is burning normal