So what your saying is for example.
A 60hp may not be as well matched. May very well use more fuel as it has to work harder to cruise along. A higher horse power engine may suit better as it doesn't have to work as hard to maintain speed. We don't need a boat that does over 30 knots that is plenty fast, our old boat wouldn't do 30 knots, but got to its top speed very quickly. Whether it was the best combo for the boat? I will never know but it did the job for us (twin 40hp). I guess we have looked at enough now just have to get out there and test some.