Chad,
A 9" prop is really too small for this motor. From the manual for this motor OS recommends 10x6-7,10.5x6,11x5-6. A 9" prop will cause the motor to over rev because of not enough load on it, and damage the motor. For the purpose of this discussion OS recommends an 11x5 prop for break in. The manual for this motor can be found at [link]http://osengines.com/manuals/40-46-65la-manual.pdf[/link].

Gboulton,
If you follow the break-in procedure that is in the manual you will do just fine, and the motor will last for a long time.

Hope this helps

Ken