This is the first time I see that Nm is quoted for an e-motor

That torque is a static quantity is often misunderstood. The units are pounds x feet or newtons x meters. Speed is not one of the parameters. Hp is force through distance with respect to time and the rpm always must be included to have any meaning.

When you pull on a torque wrench on a bolt, and say it stops at 100 pounds feet, you can hold this forever. No work is done, no power is generated. ie static.
Twist in a shaft is torque.
On a dyno, when you get a shaft turning from an engine and say you run it up to 2000 rpm without a load. Now you apply say a friction brake to the shaft attached to a moment arm and clamp down on the shaft, torque is generated, and the rpm drops, but as you want to measure the max horsepower that the engine can put out at 2000 rpm, you throw more fuel at it and try to get it up to 2000 rpm. There is a time that when you try to feed more fuel but you cannot get any more than 2000 rpm out of it. So you OBSERVE the reading on a weight scale on the moment arm and the RPM then CALULATE the horsepower. As per your equations that you supplied.

The specs above were providing specifications for max rotor speed, peak power, peak stall torque, two output powers, some can be related but some of these values cannot be integrated into formulas to get an idea of what the motor is actually doing.
Even the 12kw continuous power which is the most meaningful number if I was trying to compare a diesel engine to an electric motor needs to have an rpm stated in order to compare one to the other.

As Baeckmo has stated, "things don't line up"

If the 12 kw value is a continuous horsepower where the motor runs the most power efficient, then you need to match a diesel/gas engine where it provides the same 12 kw (16 hp) at the
most power efficient level. Then at least you can do comparisons that are meaningful

 

Thank you all, it is certainly a nice lesson in a very difficult subject. One is never too old to learn. Just to add to the above confusion. They stated 165 Ampere at peak ( 200 Ampere into the controller at 72 Volt) that indicates to me that they convert the DC 72 volt to a kind of sinus wave. Which adds additional to a lower efficiency. Thus I will never be able to know whether the statements by Ocean Volt and Torqeedo are making sense. I work with square waves, thus the losses are minimal. Heat in the copper coils are also kept low as I run the motors in transformer oil, which in turn gets cooled by sea or river water. Thanks. I enjoyed your explanations. Bert

 

Running the motor in oil instead of air will increase "friction moment" due to much higher density of the fluid. Viscosity is probably higher as well. So by solving the cooling issue (reduces efficiency at high currents) you introduced another issue (reduces efficiency especially at lower currents and high rpm).

 

I don't think so. Transformer oil is very thin and fluid. I have good results from it. It seems that Ocean Volt also has now court onto that idea, as they also have them running in a "cooling liquid" whatever that could be. No folks the only way we can get to the truth is when a boating magazine is willing to do tests. A boat with a Torqeedo motor. Then to take the same boat with a few other engines and then to do tests 1/3 power, 1/2 power 3/4 power and full power. Then we would be able to get to the reality. Bert

 

torque ( ftlbs) and horsepower is usually the same number at 5252 rpm due to the math
Torque = rpm /5252 so the graphs cross or at least meet

 

That is one way to use one type of dynamometer. Other dynamometers use water "brakes" or electric generators to provide the load, with other methods used to measure the torque.

Torque in a rotating shaft can be measured directly. For example see Ways to Measure the Force Acting on a Rotating Shaft https://measurementsensors.honeywell.com/techresources/appnotes/Pages/Ways_to_Measure_the_Force_Acting_on_a_Rotating_Shaft.aspx

 

I used the friction brake just because the principal is easy to understand. The strain gauge dyno is relatively common as it is relatively inexpensive and easy to calibrate. The one downside is
the contact points for the wire connections. Water, electric or not mentioned hydraulic are accurate but can be expensive.
We used a system in one of our labs where by a photoelectric cell pickup the twist over a given length of shaft and the time differential represented the strain (torsional deflection) This was also an inexpensive system though the accuracy at low loads on large diameter shafts was a little weak due to the sensitivity of the transducer. Much like some modern distributors on gasoline engine
This is a great article by the way