I'm sure someone will come along shortly and give a better, more detailed answer but I believe there is a part (of course I can't remember the name :-/) internal to the pump that you can flip over and it will allow the pump to be operated in the opposite rpm. I looked (very) briefly into this when I was debating rotating my snow pusher engine 180 degrees so the warm engine exhaust air would blow into the cab instead out the front. Either way, it's possible.
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-Ryan 
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