GOOD DAY! I have merc 50 that has no power on bottom 2 cylinders #3 and 4, I have replace all wires and plugs, rebuilt the carbs and fuel pump and still find that adjusting the bottom carb has no effect on operation, also pulling the plug wires independently on 3 or 4 has no effect although there is spark at plugs, if I pulled #1 or #2 wire the engine stalls. HELP!!!
