It could be the motor or it could be the auger. Can you turn the auger by hand with two hands on the big pulley when the motor stalls? What is the belt ratio of the pulleys? Is the motor accidentally wired for 230 volts instead of 115?
1hp x 5252 / 1750 rpm = 3.00 foot-pounds of torque at the motor shaft
If you have a 2 inch diameter pulley on the motor: 3.00 ft-lb x 12 inch/foot / 1 inch pulley radius = 36 pounds of pull on the belt.