There is no way to know what is the correct prop without knowing how many
rpms your turning at wide open throttle. You select prop based on max rpms.
You want the engine to run in the power band. This will be different
depending on the boat the motor is mounted on. A heavy boat will require a
smaller prop than a lighter boat.
However, a 14 diameter prop on a 50 hp engine is definetly on the large
side. I am surprised it even clears the cavitation plate or fits the
splines. Check the prop size again. My guess is it is actually an 11-3/4 x
17.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
"hdb" wrote in message
oups.com...
I have recenlty purchased a olde double hull fiberglass speedboat with
a 1972 johnson 50, I beleive the prop that it came with is incorrect.
It was a 14" by 17 pitch all the literature suggests that is a wrong
prop but I can not find any guess on what size prop should be used. Any
help wouold be nice. Thanks
Wes