Low rpm, high power calculations help
Here's a simple (frictionless) check: -

Force = mass x acceleration - with an acceleration of 0.625 m/s/s and a mass of 136 kg, that's a force of 85 newtons.

Work done in accelerating up to speed (1.25 m/s) is force x distance. 

Distance covered is average speed in that 2 second time period x 2 seconds so that's 0.625 m/s x 2 seconds = 1.25 m.

Energy inputted (work done) is therefore 85 newtons x 1.25 m = 106.25 joules.

This can be converted to power by dividing by time (2 seconds) = 53.125 watts.

So it looks like something is wrong in your calculations (or mine, god forbid!).