1976 70hp Johnson power loss

[General Lee I]

I have a 1976 70hp Johnson that we use to be able to tube and ski, now it has a hard time getting on plane.
First it would not accelerate without hitting the choke lever on take off, after take off it sounds like its not reaching full RPM. I removed and rebuilt all 3 carbs with rebuild kit and set to manual specs, the carbs seemed very clean when disassembled. I checked the fuel filter, it was clean and replaced fuel lines.
Now it will accelerate without hitting the choke lever, but still lacks take off power. new prop as of last year- same size. Fresh oil in lower unit. Replaced spark plugs with Champion QL77JC4, the old set was Autolite and wet with fuel. Cylinder compression is 135 psi on all. I tested the ignition system and it jumps a gap of 7/16"

When I run the engine in the driveway on muffs at about 1500 rpm's and choke each carb individually, the top and middle carb just about kills the engine but the bottom just slightly slows down the engine. I removed the carb and rebuilt it again thinking I may have missed something, the carb was very clean when disassembled. Put the carb back on and still have the same problem.
Is it possible that its still the bottom carb ?
Where should I go from here?
Thanks

 

[Daviet]

Re: 1976 70hp Johnson power loss

To verifiy the carb, I think you can switch the top and bottom carb, if the problem moves with the carb then you know where the problem is.

 

[General Lee I]

Re: 1976 70hp Johnson power loss

I did as you said and swapped the top and bottom carb. It idles a lot faster and ran very erratic so I couldnt tell if it helped that cylinder.
What would go bad in a carb to cause a fuel delivery problem?

 

[Daviet]

Re: 1976 70hp Johnson power loss

Stuck needle/seat, passages restricted or plugged, plugged or restricted orifices, incorrect float level.