Carburetors rich

[Jambone]

The engine will sputter in the high RPM?s and have a lot of trouble making power up top. The plugs are black and a little wet. It runs fine at idle and mid range.
How can i adjust the jetting on this 4 stroke Mercury with 4 carburetors?

 

[achris]

Rather than mess with jetting, the problem is more likely to be something else. Like restricted air flow into the air box on the front of the carbs...

Just so we can look up exactly what you have, can you give us a year, hp and serial number? Thanks....

 

[Jambone]

The year is 1995 50 hp 4 stroke. Serial # 0g254348. When I checked the compression it ranged from 135 on #4 to 150 on #1.
I was wondering if just 1 carb is faulty ie. throttle plate not opening the same could cause this. It doe's seem like an air flow problem but I am quite sure the intake is clear.