Bought a new 19" pitch, as with my 17, it was hitting 6000 RPM on 3/4 throttle. When I tried the 19, it wouldn't run past 5000 RPM and top speed was actually slower, so I went back to the 17 (18" would probably be right, but Soozook don't make them!).
Shame we didn't meet up last week - you could have tried it on the Valiant then, or I could even have dropped it off with you on my way home.
I was going to put it back on e-bay as it's too coarse for my boat, so no use to me. I already have a few 17s as spares too.