When comparing the power of an electric motor to that of a gas engine, keep in mind that when a manufacturer claims one horsepower for his .40 size glow engine, what he most likely means is that somewhere, on a cool crisp day, one of his engines managed to peak at one horsepower with an open exhaust and a tiny pylon racing prop that let the engine spin 17,000 rpm and it did it exactly one time in a row. There is a lot of pressure from marketing to inflate the rating as high as possible because the competitors are also doing it. Some engine makers, notibly Jett, simply don't give a horsepower rating because, to put it in Jett's words, "it's hard to beat the first liar".

Electric motor power is more of a "redline" than the absolute maximum. When a manufacturer rates his motor at 200 watts, it means that it is safe to use a prop and cell count that causes it to draw 200 watts of power. It can draw more for a short burst. Electrics also often use gear reducers to deliver their power to a slower turning more efficient prop. Because of this, you won't need a 746 watt motor to replace a plain bearing .40. 400 to 500 watts will do nicely.