Have a 2003 40hp Merc. Only will fire on all 3 cylinders when it's choked momentarily, then it goes back to running on 1 cylinder (center one), no power. Replaced the plugs, (no improvment) removed and cleaned carbs, (no improvment) cleaned fuel tank, (no improvment) fresh gas, (no improvment) removed drain screws on carb floats and hand pumped fuel with bulb, (seemed to flow fine) Please Help....
