Contrary to at least one post here there is a correct index position for the Cessna 150 propeller. Fig 14-1 page 14-3 also para 14-6 page 14-2 of the 100 series maintenance manual.
"On the Model 150 the propeller """MUST""" be installed to trail 30 degrees after top centre of the crankshaft"
And guess what happens, if you don't - it will be prone to vibrations ...