Doh!!
You're exactly right!
Thank you kind sir. Issue resolved!
Rick

Matt Colie wrote:
You left out the reduction to the prop shaft of 2.08 in the current
version. That leaves you over 6k with the 8".

Remember: The Honda vs everyother little bike discussion = Hondas
don't sound as fast as any 2-stoke when, in fact, are reving highter.

Matt Colie

wrote:
I'm trying to come up with an ideal prop pitch. My dealer is of No
help. And I have no tach. It's a 20hp Honda with 9.25" dia prop on a
16' planing dory. My original prop was 9" pitch which pushed the boat
about 17mph. So I went to an 8" pitch which pushes it 22mph (speed by
GPS by the way). Just listening to the revs seems a little low to me
and sure enough, I calculate 2904 rpm with my 8" prop without
considering slippage. Does anybody know how much I should add for
slippage? Recommended RPM is between 5000-6000 so I need to get 'em on
up there.
... or is there a better way to do this without a tach? (thinking
maybe I should just break down and buy one).
Any suggestions appreciated.
Thanks in advance
Rick