Originally Posted by
rickair7777
Try turning your car motor at 120 rpm by hand and see how much energy that takes.
that's a red herring, the amount of torque to turn the engine over at say 120rpm could just as easily be applied to an engine that is stuck solid.
Page 149 of naval aviators, figure 2.19 has a good diagram that shows a wind milling propeller can produce substantially less drag than a stationary unfeathered one. Note that this is for a very course prop. The converse applies for a fine pitch prop.
This is perhaps the something 'definitive' the OP requested.
https://www.faa.gov/regulations_poli.../00-80t-80.pdf