not exactly. If you keep the number of amps constant, then that would be true.

But the thing is that if you lower the number of volts a lot, the maximum number of amps may go down. (motors # of amps can be limited either by the resistance of the motor wiring or by a limit built in to the controller). At 36V, the maximum number of horsepower for that motor might be as low as 130 watts [0.17 horsepower].

This is because if electrical resistance in the motor is what limits your # of amps, then when you divide the voltage by 2, you have to divide the power you get by 2 squared (3, 3 squared, etc).

My guess (and this is only a guess) is that the motor will give satisfactory performance at 48 volts and maybe at 36 volts if you can get a gear ratio that works well for that motor.