If you put the pusher prop on the rear (clutch) side of the engine it's going to turn the wrong way. A pusher prop is designed to be turned the "normal" direction which is counterclockwise. Your prop needs to go onto the front of the engine where the flywheel and pull starter is. That is unless the engine can be run either direction which I'm sure the magneto or ignition sensor would need to be moved to facilitate this (in order to use the clutch side of the crank) but for a boat or airplane you'd want to remove as much extra "stuff" from the engine as possible to save weight.