On Sun, 05 Oct 2003 20:51:16 -0400, Gene Kearns
wrote:
I'm a bit mystified as to why I went from 150HP and a 13.75X17 prop to
140HP and a 13.75X19 prop and still run the same speed at top end!!
Not that this isn't quantifiable.... but I sure lack all of the
data...

==========================
Let's do the numbers:

SQRT 150 = 12.247

SQRT 140 = 11.832

The difference equals 0.415 which when divided by 11.832 equals about
3%. For a WOT of 30 knots, this means that you should have
theoretically gotten about 1 knot extra at the high end if everything
else matched up perfectly. The implications are that you need to
double the horsepower to go 40% faster, and that assumes no increase
in weight or drag which hardly ever happens. (SQRT 2 = 1.414)