It is not al about SC washers only. as Seadoo Service Instructions request, the complete Supercharger shaft Kit
has to be change after every 100 h !
(incl Washers, bearings, seal, etc)
If you are interested to have optimal performance The washers should be checked every 50 h and changed if the slipmoment of the SC is below specs.
All other recommendation are incorrect, and can result in SC and engine damage
