There are online prop calculators but there are still a lot of variables. Can you hit redline with your current prop? Usually you would want to step down a pitch but if you are going to a 4 blade I would step down two pitches to a 17. I would stick with aluminum, especially if you are still figuring out what you want/need. I have a merc 115 pro XS CT on a 20’ aluminum bay boat and I use a 4 blade 19p prop for fishing and a 4 blade 17p prop in the summer for mixed fishing and tubing. The different in just the change of pitch is quite noticeable, both in holes shot and top speed.
Last edited by K1500; 05/24/21.
