Wont rev revisited

[Josh791979]

Hi. 97 seadoo sportster, 717 motor.
Boat will rev up on trailer fine, but in the watee it stumbles and wont get above idle. However if i close the choke halfway it will rev and get on plane.
Took it to mechanic. He thought that maybe their was an air leak but couldnt find one, so he rebuilt boat carbs. In the process he also replaced the PTO and driveshaft cuz the splines were wasted. He didnt lake test it as he works out of his garage(he was a former pwc mechanic at a dealership)
Put it in the water today and same problem.
Took it back to mechanic and he is a little baffled.
The engine ran fine up until i put it away for winter. Its a rebuilt engine with only 1 season on it. I put fresh gas in it today.
Any ideas?

 

[XP 787]

Did he check pop off in carbs? Did he do a compression check?

 

[Josh791979]

He said the pop off spring was fine, though hes going to replace it with a lower pressure spring.
He checked the compression and it was 125/120. He said he thinks its higher though because the valve on his tester is leaking