Hi Scott, You asked about their ratings. They are accurate and probably the most realistic and accurate you'll see. If you read this page you'll see why: https://www.torqeedo.com/en/technology-and-environment/performance-and-efficiency.html Take 56%. That's very good yet you say only. If say the controller is 95%, the motor 90 average and the prop 60, then the serial efficiency is .95 x .90 x .6 = 51.3%. Now do the same for the motor you are proposing with a 60% efficient prop, so 0.9 x 0.6 = 54%. Remember efficiency is a map, not a fixed number - but for the purpose of ratings, the way they do it is good. Basically they are taking battery Watts out and looking at the bollard pull. The reason I have confidence in their ratings is I've done the measurements on my own system in the same way, so getting anything over 50% is good.
Here is Cedric Lynch's paper on the matter from about 25 years ago.
https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxwYW5vbXBoYWVhbnxneDo0ZmE5YWIyYmFkZTkxNmYy
John R
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