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Old 04-26-2012, 11:56 AM
TRBenj TRBenj is offline
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Join Date: Dec 2005
Boat: 1990 Ski Nautique
Location: NWCT
Posts: 1,149
Quote:
Originally Posted by Kyle View Post
Yes but you also told me a few months back that the blades can flex causing pitch change. How do we factor that in. My speed doesn't change past 4700-4800 so there is 300-400 rpm that are not doing anything.

Does a higher pitch flexing compensate for the lower pitch flex?
I have seen worn out props that act like youre describing. They turn consistent speed vs. rpm at skiing speeds, but flex at WOT, causing extra RPM's that dont translate to speed. I consider props like that to be either worn out (if old and springy) or simply inefficient (meaning they dont turn RPM's into speed very well at the top end).

I have little experience with the newer XMP OJ's out of the few Ive tried for the 1.23's (lower prop RPM), but I know someone who saw the exact same behavior youre describing with a new XMP on a 1:1 boat. The last few hundred RPM didnt speed the boat up.

In his opinion, the Acmes arent as susceptible to this phenomenon... they turn RPM's into speed a bit better. You may want to try a comparable sized Acme... my guess is that it will turn similar RPM's at skiing speeds, but will drop your revs slightly at WOT, if it bites and pushes the boat instead of flexing.

I would not expect a steeper prop of the same design youre using now to help performance in any way.

Last edited by TRBenj; 04-26-2012 at 12:03 PM.
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