What is the stock size prop for a 1969 20hp johnson?

Question

i would like to pick up a little speed, but i dont know what size i have or what size to go to.

Answer 1

There's only three or four props still available for this engine....when it came from the factory, most had a 91/2 X 10 three blade prop.   I think you could go down to an 7" pitch or up to a 12 Pitch, and had a choice of a bronze prop, but now, Michigan makes 9 X 7,9,10,12.  three blade.  I'd go with the standard 9 X 10.  Good luck.   Oh. The size you have is on the front face under the prop nut or if a replacement on the side.