Best store for boat prop advice?

[Bduck]

I used Willard as my lowest elevation plus it helps being a couple of miles from house to see where rpm's were with the 20 pitch. All is based on sea level performance utilizing a standard day condition which is barometric at 29.92 @ 59°. Yamaha top end rpm should be 6000-6200. I was getting 3800R's and 33mph. New prop put me at 6000R's and 40mph depending once again standard day condition. I hit a good day that particular day. Bear L I drop back maybe from 5700-5800 speed varies a little, Strawberry I hit approx 5500 with speed varying again. 
First you need to know where the manufacturer specification top end rpm should be. Then you can figure or get help to figure the prop size to help achieve this with your current info at elevation.