What is the Efficiency of Cessna-150's Propeller? From that Cessna-150's data, it used Continental 0-200-A 100 HP (75 kW) at 2,750 RPM and with Fixed Pitch propeller with its diameter=69 inches. If power is delivered maximum to the propeller (through direct shaft), then what is power of the propeller to push (thrust) the airplane?

Engine (100HP) ==> Propeller ==> Thrust (? %)

Additional Data of Cessna-150:
Weight of loaded: 680 kgs.
Weight of Empty: 437 kgs.
Wing loading: 9.4 psf (45.8 kg/m²)
Power loading: 15 lb/hp (6.81 kg/hp)
Maximum Engine Power: 100HP (75kW).
Wing Span: 10.2 m.

more detail about the plane can be seen here: http://www.skytamer.com/Cessna_150C.html
Probably quite low... After a series of gliding experiments made with a Luscombe 8E, and published by the AIAA, the conclusion was that the prop efficiency was around 62%...

https://engineering.purdue.edu/~andrisan/Courses/AAE490A_S2010/Buffer/AIAA-46372-872.pdf