Richard Casady wrote:
On Thu, 12 Feb 2009 20:46:13 -0500, D K
wrote:

The one thing I know for sure is the F90 is best
suited for a three-blade prop rather than a four.

Three is always more efficient than four. Four blades is a way to get
the blade area in a smaller diameter, if you lack space.

Casady


My admittedly limited experience with Yamaha taught me that the company
is pretty damned good matching up engines, props and boats, and that a
good dealer is also a valuable resource in prop selection. When I took
delivery of my 2008 model boat, the boat factory had just changed the
prop it spec'd for the boat and engine combo, upon a suggestion from
Yamaha. The factory sent me copies of performance print-outs for several
props. I was able to almost exactly duplicate the performance on the
factory print-out.

Almost every outboard boat I considered has performance sheets available
from the engine manufacturer, and those sheets specify props.