The Horizon web site says the Evolution 61NX "Benchmark Prop" is an APC 12x6 @ 12,000 rpm. In theory you'd have a top speed around 68 mph with '6 pitch' at that rpm.

APC makes a 13x4 and a 13x4W prop. The 'W' means wide blade. The wide blades put more load on the engine and should produce more thrust than the standard blades at a given rpm. Theoretical top speed at 12,000 with a '4 pitch' should be around 45 mph.

I have used a 13x4W on a .61 two stroke and liked it. I've never tried any 14 inch prop on one so I do not know if the engine has enough power to run one.

I currently have a 12x6 on my ASP .61 two stroke and it seems like a pretty good match on my Uproar 60. I have a 13x4, and maybe a 13x4W, in the prop box; maybe I'll try one of them in the spring.