im an RC Plane noob. i am on hobby king, i am about to order the turnigy 2730 brushless motor 1500kv and i want to know if i can get a 12 amp speed control instead of the 18 amp one. it says it pulls about 10A. im going to be running an 8x4 prop on it.
http://www.hobbyking.com/hobbyking/store/__8618__turnigy_2730_brushless_motor_1500kv.html
If you put an 8" prop on this motor, with a 12 amp esc, you'll burn out either the motor, or the esc, possibly both.
The motor is rated for a 7" or smaller prop.
The larger the prop diameter, generally the more "thrust" you're getting out of it. But pitch plays a factor too. The further apart the numbers are, the more thrust you'll get (9x3 for example) but you'll get less speed. The closer, more speed, but less thrust. (5x5 as another example) The bigger the prop is, the more amps it's going to cause the motor to draw.
Chad has mentioned he builds around the prop. So if you want that 8x4 prop, find a motor that lists something in that size.