[Rickertsen2]

They will almost definately run, but like you mentioned earlier, the power output will be greatly reduced. DC brush motors are generally not very picky about voltages. If the motors have a nameplate, try to find the manufacturer and they can prolly hook you up with the data sheet, which should have a chart that you can use to determine the power output at x voltage. If you have 4 speed controllers and they are old an you are thinking of replacing them, then you might be able to feed 24v through them if you wire 2 in series for each motor and use Y cables. This will prolly work, but no gaurentees.