Barry asked:
Hello,
This has probably been flogged to death but I am going to ask anyway.

What is the formula for calculating boat speed?

From memory the propeller pitch, engine rpm a reduction for slippage
and a couple of other things are needed.

I did have the formula on the computer but a recent crash of the
system caused it to be "misplaced"

Many thanks..

Woodchuck responded:
http://www.rbbi.com/folders/prop/propcalc.htm

Good link, Woodchuck, thanks. Nice JavaScript app. A caveat, though:
You answer is only going to be as accurate as the "Propeller Slip" figure.

Their suggestion that it's "10 to 20% slower at top speed" has an error
margin of 50%(!) Of course, they go on to say, "This ratio is found by
dividing the actual boat speed by the theoretical boat speed..." Great!
So, if you start with the actual speed, you can calculate the percent slip,
by which you can accurately determine the actual speed. *chuckle*

--
frosty (Circular Reasoning: see 'Circular Reasoning.')