I'd be surprised if the plane flew at all if you just put in an electric motor
The most important part of the electric power system is the battery. If you don't have enough Volts and Amps available at the battery, it won't matter how big the motor you put in is.
I generally regard .25-size airplanes as 10-cell conversions. 10 cells at 40 Amps is 400 Watts, plenty to give a plane that weighs up to 4 pounds healthy aerobatic performance.