I am not a big fan of running over 5K, I did with my 383 in the 22 when I put it together and was considerably slower at higher RPM's. 5600 gave me 62+ propping down to 5000 gives me 65.5, it is about torque not HP with these boat engines. I went from a 3B 21" to a 4B 23" to get my best performance so far, I plan on trying a 4B 24" to see where that puts me. Pushing a heavier you need to get on top of the torque band, a 16 or 18 not as important.
Phil
No matter what your beliefs are "GOD BLESS AMERICA"
Fully retired marine tech near 60 years in the biz.