What is the Efficiency of Cessna-150's Propeller?
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