My neighbors repair leather for a living..they have 1 machine that has a 1/3 HP motor on it! They also have a couple machines with (to me) what look like the same size and shape as the old small Singer motors. So..it has to be more than just size of the motor..after all..a motor can be huge and powerful, but if the belt and gears are not, then all you have is a big motor, I would think.