I've gotta stay with the 19P Ross, the 21 doesn't let me get enough RPM and I sold it already. So now I have two 19's, a 13" dia three and a 12 1/2" dia four. To be honest, there isn't much difference in top end between the two, maybe 1 or 2 MPH! The four launches harder and I'll keep it on the boat for a backup, and use it for tubing, etc..
I'm a little concerned about the new Solas Amita 3. After the first day on Sat the prop nut was finger loose. (The cotter pin was still in, but the tension was gone on the nut.) So I re-tightened it before going out again Sun, and when I checked it tonight it's loose again! (Cotter pin still there, just no tension on the nut at all.) The manual says to tighten the nut by hand, then turn whatever additional is required to line up the cotter pin, sound right? The four blade QL by Volvo doesn't (didn't) do that, but it has a different hub setup. (Alum. splined hub with springs) Wondering if the rubber in the Amita is compressing, will it eventually stop doing that, or what???