"Woodchuck" wrote in message
...
For me, it works very well as my props have about 8% to 10% slip and it's
verified by GPS. But then again I'm running a hi-performance boat over
100mph. The props I have are Mercury stainless steel lab cleavers. Most
average consumer props have alot 15% slip for stainless steel and near 20%
for aluminum. The calculation provides a good starting point when you
want to change pitch, RPM, mph, etc

No one has asked the obvious question - why would anyone want to calculate
boat speed this way?

--
Peter Aitken