Hello everyone new to the site and PWC's

I just bought a ski and i'm having 2 issues with it.

1.) It does 50 and won't go over 4,000rpm and i thought i read it should go quicker and rpm's should be higher?

2.) it just started taking in water from the rear of the ski as i'm putting it in the water. Could it be the drive shaft coupler?

Thanks and any help is appreciated.