Hi Yak13,

Here are the spare parts list for converting YS91-SR to prop;

Drive Washer Retainer - F9324
Drive Washer - F9323
Tru Turn Prop Nut - TT-0813-A



I converted this engine some time ago, did not take any RPM readings, used this engine with pipe in a 1.77 metre aerobatic model and all I can say is take some bike clips with you!!
Hope this helps.

Sydc