On Sat, 12 May 2007 11:47:05 -0700, Josh Assing
wrote:

Two people (one I consider knowledgeable and one from a shop I use regularly)
said "that's not enough clearance, should be about 10% of the prop diameter"

And ten percent of a 15 inch diameter prop would be what?

That is way to close for a number of reasons including cavitation.

What you are looking for is a 14.5/21p or thereabouts - might need a
19p - doubt if you will need a 23.