changing prop size or pitch on mastercraft
Foot4fun
on inboards. I have a 92 prostar 190 with 285HP. The boat turns 5300 rpm
with a 13X13 bronze prop. I would like to get the rpm down to 4900-5000
max.
Has anyone tried one of the new stainless three or four blade props for
inboards
or going to a 13X14 bronze, and how did this change the performance and
wake ?
Michael A. Donato
Well, you could go the 13x14, or even a 14x16 by Nibral or Michigan. As far as
I know, the size of your prop shouldn't affect your wake. What a larger prop
does, is it creates a slower "hole shot" and a higher top end speed, where as
a smaller prop will do just the opposite. I don't know exactly how much a
larger prop will turn your rpm's down, but i would image it would be pretty
good. As far as the new stainless steel props, my opinion is to stay away
from them. Stainless steel flexes a lot more than brass, therefore, you won't
get the performance out of it that you would from a brass. Also, the reason
inboards have always come with brass props, is that the torque created by the
inboards rip the stainless steel props apart. The stainless steel props also
make it difficult to repair when damaged. Now that I've ripped apart the
stainless steel props, let me say this, although I know they won't perform
like a brass prop, they would probably make a good spare since they are just
a small fraction of the cost of the brass. Take it easy, and if you have
any more questions, let me know.
-Mike Donato
don...@indy.net
Skip Frank
> In article <3cap0j$8...@newsbf01.news.aol.com>, foot...@aol.com
(Foot4fun) says:
> >
> >Has anyone experimented with changing the pitch or diameter of their prop
> >on inboards. I have a 92 prostar 190 with 285HP.
>Has anyone tried one of the new stainless
> As far as the new stainless steel props, my opinion is to stay away
> from them. Stainless steel flexes a lot more than brass, therefore, you won't
> get the performance out of it that you would from a brass.
I agree with Mike about the stainless prop and speak from experience. I
own a 91 ProStar. It came stock with a stainless 13 x 13. Up until then,
Mastercraft used Nibrals and that's what I had on my 87, which I sold.
The stainless prop made a weird noise and vibrated. I noticed that it was
coming from the prop because I had a spare Nibral which I used while
repairing a couple of dings in the stainless. I talked to the dealer
about it and the factory replaced the stainless with a brand new Nibral.
They switched back to using Nibral because of other similiar complaints.
If you do experiment with another prop, stick with Nibral. It's a softer
material, but it performs better on the Mastercarft.
--
Skip Frank
Barefootr
<<<<As far as I know, the size of your prop shouldn't affect your wake.
What a larger prop does, is it creates a slower "hole shot" and a higher
top end speed, where as a smaller prop will do just the opposite.....<>...
As far as the new stainless steel props, my opinion is to stay away from
them. Stainless steel flexes a lot more than brass, therefore, you won't
get the performance out of it that you would from a brass. Also, the
reason inboards have always come with brass props, is that the torque
created by the inboards rip the stainless steel props apart. The
stainless steel props also make it difficult to repair when damaged. Now
that I've ripped apart the stainless steel props, let me say this,
although I know they won't perform like a brass prop, they would probably
make a good spare since they are just a small fraction of the cost of the
brass.>>>>
My comment is this: Untrue, True, Untrue, Untrue.
1) The size of the prop *will* affect your wake turbulence. Even a minor
thing like a bad center fin will affect your wake.
2) Yes, a larger pitch prop will give a higher top end, with a slower
hole-shot.
3) Stainless props *FLEX LESS* then brass! Brass is a very soft and
malable material, and every prop guy has told me the same thing. Under
torque, a brass prop will "give" in to the power, and deform slightly due
to the stresses on the prop. A stainless prop will not. Stainless is
extremely hard (compared to brass) and therefore, if you were to have a
prop strike, you are likely to damage *more* than just the prop, (like a
bent shaft) whereas a brass prop will just fold the blades up. If a
Stainless prop is not tuned or balanced correctly, it will give more
vibration, also due to this stiffness. And yes, Stainless props are "near
un-repairable."
4) The power from inboard tournament boats will *not* rip a stainless prop
apart. The props that have been having problems are the latest
multi-blades....anything over 3. Very few of the 4 bladed stainless are
staying together on an inboard. (Hence the fact that no boat from the
factory is equipped with a 4-blade) This is in difference to the
"hi-five's" on outboards like the Flightcraft Barefooter, which perfroms
wonderfully.
5) Last but not least, good stainless props are *more* expensive than a
brass unit.
Hope this helps.
Bare. :)
Michael A. Donato
Bare,
I stand corrected. When I look back at what I said about "ripping" the stainless
apart, I think I got confused and I crossed stainless steel with aluminum. In fact,
thank you for the quick lesson. I guess we do learn something new everyday!
-Mike Donato
don...@indy.net
Larry Brown
(Skip Frank) writes:
>The stainless prop made a weird noise and vibrated. I noticed that it
was
>coming from the prop because I had a spare Nibral which I used while
>repairing a couple of dings in the stainless. I talked to the dealer
>about it and the factory replaced the stainless with a brand new
Nibral.
I have an older Mastercraft that came with a Nibral 13 X 13. I
switched to a Stainless 13 X 13. I also noticed the strange noise,
especially when making a tight turn to retrieve a fallen skier. I don't
notice any vibration.
I picked up about 2 mph with the SS prop, although that is not the
reason I switched.
The reason I got the SS was durability. In the spring, the resevoir
we ski at has a lot of floating debris. These are wood pieces ranging
from small sticks to large stumps. (A few years back, I broke an 8" dia.
log in two with my friends outboard. It was floating just under the
surface) In three summers of skiing there, I haven't damaged the SS
prop. And I have hit a lot of debris, although I have managed to miss
the 8" logs and stumps. With my old outboard and aluminum props, we
would budget in a prop repair for each trip!
I would imagine that if I hit a rock or something with SS, it could
damage more than hitting the same thing with Nibral. But if you boat in
an area with a lot of floating wood, the SS can be a good investment.
Larry
--
Larry Brown lar...@ix.netcom.com
James Siegrist
Where did you get your information about all the different kind of props and
which is best?
foot4fun: chances are your your Prostar came with a Nibral as standard. It
stands for Nickle Brass Alloy.
Stiffness should be as follows 1) Stainless 2)Nibral 3)Brass. Stainless with
the less flex should give you the best performance. Bent stainless props
being less flexible will not be able to be reworked very many times without
it coming apart do to stress fractures. Nibral props can be straightened
many times after being bent. Brass props just through them away or keep as a
spare.
I would have to say that Mastercraft has most likely done a lot of testing
with prop sizes and pitch for their boats. My suggestion is to stay with the
prop that came on the boat and don't waste your money on the experimentation.
You will probably end up with a shelf full of props that you won't use. If
you don't want to over rev the engine just slow down a little bit. I take it
that if you wanted a speed boat you wouldn't have bought a Mastercraft. If
you want speed go buy a jet boat. :)
Jim
Bill Walker
[a bunch of stuff with which I agree, and...]
> 3) Stainless props *FLEX LESS* then brass! Brass is a very soft and
> malable material, and every prop guy has told me the same thing. Under
> torque, a brass prop will "give" in to the power, and deform slightly due
> to the stresses on the prop. A stainless prop will not. Stainless is
> extremely hard (compared to brass) and therefore, if you were to have a
> prop strike, you are likely to damage *more* than just the prop, (like a
> bent shaft) whereas a brass prop will just fold the blades up. If a
> Stainless prop is not tuned or balanced correctly, it will give more
> vibration, also due to this stiffness. And yes, Stainless props are "near
> un-repairable."
I agree completely with everything in the above, excepting I believe the
material that all these posts are calling "brass" is really "bronze" ("an
alloy of copper and tin", according to Webster. Brass is copper and
zinc). Brass is way too soft to use for a propellor. And I believe
Nibral, which is what most of the tourney boat props are made of, is a
NIckel-BRonze-ALloy, not a nickel-brass-alloy.
You'll note that one of the well-known prehistoric ages is the Bronze
Age. If it'd been the Brass Age, we'd all still be living in caves and
waterskiing behind mastodons. :-)
----------
Bill Walker - WWa...@qualcomm.com - QUALCOMM, Inc., San Diego, CA USA
"First thing we do, we kill all the lawyers." - Shakespeare