What the circuit breaker does is protect your motor from drawing too much amperage if it should ever be run under a heavy load. Electric motors rely on Volts for RPM and but have the potential to drop and LOT of amperage across the armature if forced. It's the same rule as a car: Running on flat ground at high speed doesn't require a lot a torque just engine speed to keep up the momentum. As soon as you hit a hill your car slows down and you press further down the gas pedal in order to maintain speed, this is when torque (amperage) comes into play.
The first thing that might come to mind is your battery: You might wonder if your battery can even supply 60 amps (if it can't thereby negating your need for a 60 amp breaker) but it has to be able to supply 60 amps or the demand by your motor will burn it up.
If your manual claims you need a 60 amp breaker, get one. However if you can't find one but can find one that is rated close to it you can make sure it is enough by determining the amp rating of your motor either by stickers on the motor itself, technical specs in the back of your manual or by consulting the manufacturer personally. Running one won't harm your motor as it will just trigger prematurely and rob your motor of it's full potential. However do not go over 60 amps, because this can obviously burn up your motor. The ratings on motors are conservative numbers and you can fudge it a little, but don't because over time it will drastically lower the life of your unit.
Good luck!
