Go with the a 16" or 17".
I have a 20 Seafari,(heavier) and I run a custom 16.5" pitch 14" diameter 3 blade
Powertech Prop (with this rake/blade design) on a reman'd 150 carb Merc that hydrodyno's at 187 hp at the propshaft. I turn slightly over 6000 rpms at WOT at 43 knots on the GPS, jacked and trimmed. I also have a Bob's nosecone installed. That alone added about 2-3 mph to my speed. (It came installed on my "new" lower unit after I used the old one to strike a floating log at 30 mph in the dark )
If you want a custom prop made just for your boat, PowerTech also enjoys making custom props, as long as you're not talking in excess of 27" pitch.
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury