Josh Assing wrote:
19p isn't giving me the correct wot rpm range.



That's an important piece of information you left out of your original
post. What are your numbers now? What boat/weight/engine/gear ratio?

Still, if you don't need the additional surface area of a 4 blade, it is
beyond superfluous.

It sounds like you should move to a quality 17P SS 3 blade wheel. The
prop design and your gear ratio will determine how much of a change will
occur.

Every prop is a compromise of sorts.

The most efficient prop is a one blade. They're a bear to balance, though.

2 blades are more efficient than 3, and are fine for very light planing
hulls(like hydros) that do not rely on a large surface area. Balancing
is still critical.

A 3 blade is a good compromise of surface area, balancing ease, weight,
& efficiency. 3 blade props have the widest choice of
shapes/profiles/cupping designs available.

4 & 5 blades are really specialty props for specific applications where
the extra surface area & ease of balancing are important, & weight is
not. The CNC'd 4 blade ski props, for example, are super-smooth &
quiet, and on a tournament hull very little if any top end is sacrificed.

A 4 blade can also help on certain planing hull designs where porpoising
is prevalent even with minimal trim-out.

You really need to know what your goal is in selecting a prop. The
ability to try several different styles would be a huge advantage. I
have one shop down in the Finger Lakes that has allowed me to do this
over the years.

Rob


On Wed, 25 Apr 2007 21:29:36 -0400, trainfan1 wrote:

Josh Assing wrote:
The local prop shop says that the Revolution4 (17 pitch) will yeild similar WOT
as my SS 3 blade (19 pitch) and recommended the apollo 4 blade SS in 16 pitch

That seems like a lot to drop -- and seems like it'd make my top end & midrange
suffer.

The mercury prop selector pushes the rev4 17; and I just can't find any other
prop-calculators...

They weren't too thrilled about me "trying the prop" and 'would have to get back
to me'

Thoughts on this mojo-prop-magic ?

-j

If you don't need the additional surface area of a 4 blade, it is beyond
superfluous, it is a burden.

It sounds like you should stick with the 19P SS wheel. There are many
choices in that spec alone, even from just Quicksilver.

Rob