650 sj issue

Location
Nor Cal
Looking for some direction with this.
When you are half throttle to full the ski only gets to about 10 mph. It surges up and down not gaining any speed. If you jump the ski out of the water it takes off and runs fine until you let off the throttle and it'll go back the same thing. first we thought it was fuel so I cut out any places there might be any leaks fuel switch, primer, did a rebuild kit on the carb changed the fuel filter and checked the check valve. compression 150 each cylinder
its got a b pipe, and port work.
jets are 120, 162.5 main and 2.5 needle I understand those are big but its what was in it originally when I got it.
Anything helps thanks guys
 
Location
US
Did you check or rebuild the fuel pump? I've had a similar issue and it was a bad diaphragm in the pump. When we checked It it looked good. We replaced it anyway and it ran like a champ after that. Ive since had had my motor blow so I'm rebuilding slowly.

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Location
Nor Cal
The diaphram on the other side of the carb as the jets? I rebuilt that ended up yanking the motor out yesterday and changed the crank seals so we will see if that fixes it.
 
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