Donald Watts are Volts time Amps pulled. To answer your question you need to provide the battery voltage you will use and the load, i.e. the prop diameter and pitch, and its expected amp draw. Of course the retailer should have already provided a chart with the recommended props for the voltages this motor can handle. Since they don't, it's up to you to guess that and hope you're right!

Donald Brushless motors wires do not have polarity like brushed motors. The 3 wires alternately pulse each set of magnets inside the motor acting more like AC current, not DC current. As already mentioned, swapping any 2 of the 3 wires changes direction of the motor. Some ESC programmers can also do that without changing wires.

Donald Most BL motors can spin in either direction by changing any 2 of the 3 wires powering it. But if the motor spins the same direction as the prop nut, the nut will eventually spin itself off the prop shaft unless you use a Nyloc nut or secure the nut after it's on so that it cannot move unless you remove the wire or the clevis pin. Some use a second nut over the first but a liquid like Locktite should be used in that case.

Donald The specs only show up to 4S. You will most likely burn up the motor is you use a battery higher than 4 cells.

Donald The flat spot is for the gear to be as shown in the picture ad. If you rotate the strut, the flat spot will not be engaged and the entire strut and wheel will rotate very easily. ONLY USE as shown in the ad.