Hi this is Kenny, who am I speaking to ?
It can be a few things, what stand out is definitely a impeller/pump issue that has been compromised (rock damage) if the ski is on the trailer you need to crawl up under it with a flashlight and then look up into the pump tunnel towards the rear of the ski, at that point you should be able to get a good birds eye view of the leading edges of the impeller, you'll know at that point of the leading edges are damaged, then follow it out to the outside diameter of the impeller and that will be your wear ring. What happens so often is a rock or debris will get wedged between the outside diameter of the prop and the liner and dig a deep groove in the liner, then that needs to be replaced.
Impellors from BRP are around $300 and wear rings are about $70, you also have the option of getting your damaged prop repaired, a company in Calimesa Ca, Scat-Trak Performance, they do an excellent job on getting your prop reconditioned and it will come back with a little more performance, I've had them do hundreds for me and most likely they are the manufacture of the prop that came in your ski from Seadoo, if you go with them you can knock off about a $100 rather then the $300 you'll pay for a new one, I don't recommend Solas Impellers.
This is a good place to start and is usually the case, let me know of you have any further questions