It is a trait of the SeaDoo because there is no 'transmission' or lower unit or whatever that actually stops a prop from spinning. It really bugged me at first...I had the same problem at the dock.
I fixed mine. It doesn't creep anymore. I adjsted the linkage at the reverse gate. Droppping it just a bit caused it to equalize the forward and back thrust. The adjustment is simple although it is in a tight spot. You'll need a 10mm wrench.
Look for where the reverse cable hooks to the reverse gate (starboard side of jet). The adjustment is made close to where cable gose through the hull.
Take note of where your reverse gate is positioned in neutral.
Unhook the clip holding on the rubber sheath covering the cable and slide the sheath toward you. Remove the two 10mm nuts on the bracket holding the adjustment. Back the 'funky' looking adjustment nut out (maybe) two turns and re-assemble.
Make sure the gate has dropped just a touch in neutral from where it was before the adjustment.
It may take two or three tries of adjusting and testing in the water before you get it right.
