This was linked for my by a mod when I had to go and get a new one for my boat, very helpful and simple.https://www.discoverboating.com/resourc ... ller-pitch
I ended up getting a 23 as speed wasn't important to me for what is was doing.
Synopsis was" A lower-pitch prop is like low gear in a car or a bicycle—you’ll accelerate quickly but top speed will suffer. A prop with too much pitch may deliver more top speed because the prop moves further forward with each rotation, but acceleration may be poor and the boat will struggle to get on plane."
I have a 23 on a 125HP engine, which might actually be a little high pitch-wise, I should prob have a 21 but there is usally not more than 2 in the boat
and I rarely run at full steam.