The motor by nature is going to have a high starting current. In your application it also has a heavy load. It sounds like the power distribution is marginal and you are probably suffering from voltage drop. The voltage drop will exacerbate the starting challenge of that loaded motor and you probably never get off the starting winding before the circuit trips.
Going to a smaller pulley may gibe it some advantage. If you can add a clutching idler to the drive belt you can get the motor up to speed before applying the load.
Since you seem to be on the correct voltage a boost transformer probably won't help since you seem to be having trouble pulling enough wattage through the line.
Does the motor have a starting capacitor? An old Maytag washer repair trick was to add a capacitor to the starting winding when the motor when it was showing its age. That will boost the phase shift between the windings sets and with that the starting torque.
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