Although I don't know the cu in of the pump, A large pump will only draw the power it needs to operate. As soon as the pump is turning, it has potential pressure, and if the pump is running at low volume, 2 or 4 GPM's, it still is going to get the work done. The larger pump only becomes a problem, when it is running at full rpm, and you put a heavy load on the system, then the pump may stall the engine, because it now requires more HP, which you don't have. Once you know what that limit is, you can operate within set parameters.