My BME 100 has two holes tapped for #6 screws in the drive washer. Apparently you are to put two #6 machine screws in there as drive pins for the prop. Every time I put the screws in there they sheer when I run it. Whats the solution for this? I tried to leave them out and torque the prop nut to 50 ft-lbs but it has thrown the prop and I am afraid to get in front of it to start it