Larry Jaques wrote:
Although a smaller pulley will -somewhat- reduce the load on the
motor, it will -primarily- just reduce the pump speed. ...

Are you sure? It seems to me:
motor load = its speed x torque
torque = pulley radius x belt tension
belt tension = pump torque / pump pulley radius

load = speed x pulley radius x pump torque / pump pulley radius

The only way that motor load isn't a linear function of its pulley size
is if the pump torque isn't constant with its speed. I.e., if pump
torque goes *up* as its speed goes down.

Am I missing something,
Bob