I am not very informed on the subject,I would hope to find some help
on how to understand the wattage of an unknown
motor I have on my ebike.
I bought it second hand and there is no information about it written
on the motor itself as it often is written on other motors.
Other than that if the Voltage and Watts rating are not on the motor then I do not know of any way to find out what they are.
Oh one thing I just thought of is to look at the controller and see if it has a Watts rating printed on a sticker on it.
If still no luck then maybe insert a photo of the ebike here and see if anyone else knows what make and model it is.
Please let us know how it goes.