Well, ya learn something every day. Thanks for the info!

--Mike

"tony thomas" wrote in message
news:yu6%d.88068$Ze3.87319@attbi_s51...
Actually they do make variable pitch props. They are very expensive
compared to regular props (even more than a high performance prop),
require maintenance on the springs and cams, and are less efficient on top
end due to blow by at the hub. However, they do work for overall use on a
runabout. Most people just won't spend the money to get one.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
"mgg" wrote in message
om...
As Tony said, you need to judge it based on your RPMs at wide open
throttle (WOT). You need to find the specs for your engine and see what
the RPM range is at WOT. If your boat currently revs higher than the
spec, you need to increase the pitch of the prop. A general rule of thumb
is that each number increase of pitch will reduce WOT by about 200rpm.

I bought a boat last year that ran at 5500rpm WOT. The manual said
4400-4800 was optimal. I suspect that the previous owner bought a lower
pitch throttle to pull a good sized skier out of the water. I put a 23
pitch (from a 19) on the boat, and it purrs along at about 4600rpm
WOT...perfect.

Now, if we could just have variable pitched props like airplanes, all
would be good with the boating world. g

--Mike

"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