you use a prop adapter that is either supplied with the motor, the prop or is purchased separately. I believe the GWS packages come with the prop adapter.
ITEM : GW/EDP-300A1
MOTOR : EM300
WEIGHT : 49g (1.73 oz)
W/EM300 MOTOR , EP4530 PROPELLER *1
Factory standard product : GW/EDP300A1(EP4530) Spec of other propellers are reference for optional purchase.
Comes with a sheet that reflects the chart on this page:
HOW TO READ THE GWS CHARTS
You look down the left side of the chart. Those are prop sizes. A 4530 is a 4.5" prop with a 3 inch pitch. Look over one column and see the battery voltages they tested it with and the amps that the combo draws.
Lines in red mean that that voltage/amp/prop combo will damage the motor.
HOW TO APPLY THE WATTS COLUMN
The power column, W = watts of input power. That is what you use to figure watts/pound using the full weight of the plane in ready to fly configuration.
EP4530, 7.2V 10.1A and 72.72 watts input power.
In a 1 pound plane with this motor and this combo, you would have 72.72 watts per pound.
BRUSHED VS BRUSHLESS INPUT WATTS
The efficency numbers they give are NOT the efficency that we talk about when we discuss brushed vs brushless efficency. That is entierely different.
As a rough rule, brushed motors are about 50% efficent. Brushless about 80% efficent.
So a 72 watt brushed motor delivers about 36 watts to the prop and wastes 36 watts as heat.
72 Brushed watts, as I call them, will fly the plane but with mild performance.
A 72 watt brushless motor delivers about 57 watts to the prop and waists about 15 watts as heat.
THAT'S WHY BRUSHLESS MOTORS ARE WORTH THEIR HIGHER PRICE
So the brushelss motor will give you better performance for the same amount of power used.
72 brushless watts, as I call them, will deliver a lot more performance, greater speed, better climbs, etc. Or it will deliver the same performance using a lower throttle setting, thus the battery pack will last longer.
Hope that makes sense.