Any place you are going to buy from will be able to tell you but basically
if the 19 is the right prop rpm wise then you will stay w/ a 19. The
diameter will be less than the 14.5 to make up for the extra blade surface
area.
If you need about 150 more rpms you can go to an 18.


--
Tony
my boats at http://t.thomas.home.mchsi.com

"John Davison" wrote in message
om...
I have a 3 blade 14.5x19 aluminum prop on my 200 HP Mercury Blackmax.
How do I determine the equivalent 4 blade prop? (I'm assuming a
14.5x19 3 blade prop is not equivalent to a 14.5x19 4 blade prop.)

-- John