I am using a AXI 2826/12 electric motor.

Specs: http://www.hobby-lobby.com/brushless-axi2826.htm
760 Kv (RPM/V)
10-18 Ni, 3-5 Lipo, 12 Ni battery = 14X7 prop
4S lipo battery = 13X8 prop
5S lipo battery = 11x6 prop
40Amp ESC
For 53 – 106 oz planes
Good for .40 - .46 trainers

I am currently using a 13x6.5 prop