Understanding electrical specs...
When computing the HP of a motor, you have to account for efficiency and startup issues. In your case, the original specs state that the motor draws 3A, which could mean that at full load, the motor draws 3*120 = 360 watts. This is not the actual available power, which is always going to be less due to efficiency losses, so the actual available power may be close to 285/300 watts as shown.
The numbers on the actual motor don't make a lot of sense. However, when sharpening a chainsaw blade, you don't need a lot of power, you need a tool which has a sharp file of the proper size, accurate adjustments for the various angles, and a good grip on the bar. Too much power will ruin the blade quickly. I sharpen mine using a clamp on, hand drawn system that works very nicely.