150 Merc bogging out @ 2000rpm under load

Hi all. I've got a mid 70s 150 Merc L6 that is bogging out under load. If it's just me in the boat, it seems alright. I've checked or replaced the following with no improvement: All plugs replaced, distributor seems fine, I've rebuilt the fuel pump (gaskets, diaphram, check valves)checked the fuel line from tank to pump, compression is good across all 6 cylinders. The one thing that was odd was that I can choke out the engine by adjusting the idle mixture screws on the top and middle carbs but when I try the same thing on the bottom one, nothing happens. This prompted me to pull that carb and give it a good inspection and cleaning. Everything looked ok. Any suggestions would be greatly appreciated.

Re: 150 Merc bogging out @ 2000rpm under load

I would put in new neddles and seats in it.<br />New floats too unless they are the hollow plastic<br />ones in it now. course if there is gas in one of them replace it. Then try it, is it still works<br />the same way check for crankcase leaks on the lower two cyls. If non you may have a broken reed valve.<br />Good Luck<br />corm