Swath,
You need a dynomometerr to measure the torque. While the no-load charachteristics are a good place to start I think you need to develop a torqu curve to determine how it will run at different speeds/loads.
As an example, here's a typical torque curve from an electric motor (not the ones we are using but it was the quickest I could find for this post). These will vary greatly from motor to motor. It would be interesting to see the torque curves for both motors.