rplumbo is correct. The APC 14x4W is a good one on a well broken in 63 running 20% or more nitro. I used one last year, and I was turning it at about 9600-9800 if I recall. I'm using Wildcat YS 20/20. I certainly would not even try to run my YS on 10%. I tried 15% Omega once, but the performance gain on the 20/20 is noticable. The main thought that keeps surfacing is that you will see a good gain by going from 15 to 20%, and a bit more if you go to 30%. I'm just too cheap to pay for the 30%.

Dave believes that the 63 is happiest at 10-11K, as already stated, so with that in mind I purchased an APC 13x4W to try. It should spool up faster and let the 63 let loose a bit.

Central Hobbies carries both of these props.

Oh, forget the APC 13x4 "regular" prop. It turns about the same on my 46FX as a 13.25x3.75. You want the 13x4W

Chuck