96 200 Oceanrunner wont rev over 4600 RPM

[easterly]

I have a 1996 200 Johnson Oceanrunner that won't rev over 4600 RPM. Replaced stator and VRO pump 2 years ago. Since problem has arisen this year I have rebuilt carbs, switched fuel pickups, run on a separate fuel tank, changed fuel filters, replaced the power pack, replaced the ignition base. Motor used to run at 5600 RPM last year. Compression is fine as well. had two different mechanics test it as well as myself. I have checked the carbs and the are opening all the way up at WOT. Not sure what to do next....

 

[SilverSS07]

Did you do a spark test to see if it jumps 7/16's gap? Have you done a drop test?

 

[easterly]

Have done a drop test, firing on all cylinders. Have not done a spark test to see if it jumps 7/16's gap

 

[easterly]

Also all new Champion plugs