Wow is what you might be saying when you see the repair bill from an authorized seadoo dealer to fix what this hack mechanic messed up on your boat.
Seriously though, it sounds like this person has no business touching a seadoo craft. If anything on the throttle body (like the idle set screw) has been tampered with it will need to be completely reset and reprogrammed by someone who has the proper seadoo software.
I can only hope your mechanic did not have enough time to screw anything up and this does not turn out to be an expensive lesson, but if your boat is not running correctly you know who to blame and will need to find a new repair facility.
If you would like any additional information about the throttle body and the reset procedure you can download a copy of the shop manual, there is a whole section and specific procedure to do this. Click the link above that says 'seadoo manuals'