Superjet bogging down

I have a 650 superjet and it sounds like it hits rev limiter at about 1/4 to half throttle. It will bog down and not rev when the throttle is pulled. It does this in and out of the water.. what could be the cause of this?
 
It is single carb. I have played with upper and lower adjustments and haven’t noticed a change. Set back to stock and made some tweaks.. ski is far from stock though and not too sure on how to tune it properly.
 
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