Underprop your boat for great performance! Modern engines have electronic protection against excess rpm so there is no reason to worry. I was going to a 17" on a 140hp Suzuki DF140 on a 18' hull that was a dog. Not a 2-stroke definitely. Anyway, the box mistakenly contained a 15" so I gave it a try. Dynamite! Might get up on a slalom ski behind this boat. All these years I've been propping for red line when trimmed out at WOT. Why? Guests generally hate a fast, bumpy ride; especially in a light OB. It was to prevent the engine from overrevving and blowing up, I guess. Now engines have electronic rev limiters so, why worry? Trimmed out, Mr. Suzuki says "No more! at 6500 rpm." 4" of pitch reduction made a sports boat out of this old fisher. The Suzuki can protect itself and doesn't need the old incremental approach in prop selection.