Why an SS prop?

chris4x4

Seaman Apprentice
Joined
Dec 22, 2007
Messages
34
What is the big deal of getting an SS prop? New and just wondering. Thanks!:)
 

oops!

Supreme Mariner
Joined
Oct 18, 2007
Messages
12,932
Re: Why an SS prop?

hey chris

welcome to i boats
and merry christmas,

great people here, VERY knolageable.

just about any question you wanna ask has been covered in these fourms.

just hit the search button, and there you go!

in answer to your question, i havent used ss yet. but am about to next season.

props "slip" (cavitate) in the water. sometimes as much as 15% uasually a alum is 10% at W.O.T (Wide Open Throttle)

ss props are much less uasually 5%. that can mean a few miles per hour at top speed. and u get a stronger hole shot too. good for skiing.

alum props also "flex" a bit. and that also hurts your over all performance.

down side is....if you whack one....warm up the visa card!

hope that helps.

also. about i boats. you might wanna give posters rules a quick once over. its real common sence stuff, but good to review it once in a while.
this forum is fantastic ! u wanna ask a motor question? 20 vetran mechanics from all over the globe answer you in just a few hours. sometimes in seconds!

and dockside chat is a neat place to just talk and have a few laughs!

welcome
cheers
oops
 

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: Why an SS prop?

Not to beat you up ooops, but I want to clarify a few things, . . . SS props of the same pitch usually give worse hole shot than aluminum because of flex. Think of the aluminum as flexing to a lower pitch giving better hole shot, the downside is they stay flexed, so "slip" more, when in fact the issue is they are not getting their full pitch due to the flex. Also nothing but the most amazing and lightest race boats get 5% slip. You're doing really well to get down to 10% ;)

The biggest advantage to SS is that the blades can be made thinner with little flex, so they are hydronamically more efficient.
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Why an SS prop?

Just to add what I know, and learned, about SS props. Being as rigid as they are (less flex) then aluminum, they give you truer pitch at all speeds, meaning more top speed, if you have the power to spin them, that's why most people see an increase of speed, they push more water, also they tend to hold their speed better at all times, meaning at any throttle setting, they are more likely to keep the same speed without wavering (sort of like a cruise control effect). They also don't ding as easily, but the disadvantages are, they are less forgiving on your drive system if you hit something while running, and they are heavy, so you lose a slight bit of power just spinning them, and finally they are expensive. For these last reasons, usually you have to downsize one number in pitch then aluminum to run them, but it is always worth it IMO
 
D

DJ

Guest
Re: Why an SS prop?

Not to beat you up ooops, but I want to clarify a few things, . . . SS props of the same pitch usually give worse hole shot than aluminum because of flex. Think of the aluminum as flexing to a lower pitch giving better hole shot, the downside is they stay flexed, so "slip" more, when in fact the issue is they are not getting their full pitch due to the flex. Also nothing but the most amazing and lightest race boats get 5% slip. You're doing really well to get down to 10% ;)

The biggest advantage to SS is that the blades can be made thinner with little flex, so they are hydronamically more efficient.

Absolutely correct. What QC said. ^^^^^^^^^
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Why an SS prop?

Some install SS because of the "bling" -- and probably with no idea whether or not it's the right prop. Their reasoning is that "I got it cheap on E-bay and it fits, therefore it must be ok."
 

EMM

Seaman Apprentice
Joined
Dec 24, 2007
Messages
42
Re: Why an SS prop?

SS props are stronger therefore the blade profile is slimmer so the prop has less drag which helps make up for the extra weight. They also won erode as fast as alum. Alum is cheaper to buy if you do ding it and they are easer on your drive line if you smack something, however if you have to have a bushing pressed in an alum. it usually splits unlike SS. I run a SS prop and my slip is only about 2.5-3%
 

chris4x4

Seaman Apprentice
Joined
Dec 22, 2007
Messages
34
Re: Why an SS prop?

Thank you for the replies folks! And Merry Christmas! Sorry for not searching. I know better. I guess what Im curious to know is if an SS prop is worth the extra money. Im only running 120 h.p. and with a full boat Im at 48 m.p.h. Think an SS prop would show significant gains?
Thanks again!:)
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Why an SS prop?

If you understand what I wrote, then you'd know that even though you're doing 48mph WOT your aluminum prop is flexing under load, SS won't flex near as much, so it will pump more water, what do you think will happen?
Hence more speed!
 

chris4x4

Seaman Apprentice
Joined
Dec 22, 2007
Messages
34
Re: Why an SS prop?

Thank you for the information. Being new to boating, I wasnt sure what the "flex" was or how it was affecting the boat. Thanks agian for the help. :)
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Why an SS prop?

Not knowing what RPM the engine currently runs at wide open throttle is critical in determining whether a different prop, aluminum or stainless, has any benefit. If your engine is already turning at its recommended wide open throttle rpm with an average load you have the correct prop. Simply going to stainless steel is no guarantee you will go faster, have better hole shot, or both.
 

walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: Why an SS prop?

Silvertip has a good point...it's hard to give advice on a prop choice without knowing boat/hull style, max recommended hp vs. actual hp and what not only your speed is now with WHAT prop-not just pitch, but make and model as well, but most importantly, what RPM are you turning "X" prop with a normal load, and are there any short-comings that you notice performance-wise as it is now.
Also, I will back QC on the slip....15-18% is common-place for aluminum and if we get lucky, we can get down to as good as 10% with a quality SS prop in the right application...sometimes 1-2% less than that depending on hull style.
 

chris4x4

Seaman Apprentice
Joined
Dec 22, 2007
Messages
34
Re: Why an SS prop?

Good points, you guys. Once again I find myself learning more and more. The boat is a 1997 Bayliner Capri 17'. Max h.p. is 120. It has a Force 120 out board and the factory stock prop. At 48 m.p.h. the engine is turning 5100 rpm. Performance seems great, but as this is my first boat, I dont have an accurate barometer to gauge by. Thanks, again, for all the help folks.
Merry Christmas!
 

walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: Why an SS prop?

Merry Christmas to you as well!
The 120 Force/Merc has a max recommended RPM of 5250....in 1997.
With todays fuel, I would say target 5400 with a normal load.
That being said, a good quality SS in 2" less pitch would bring your R's up slightly with a speed gain over what you have now...the problem at hand is the prop I was going to recommend is not available for the Force/Crysler shaft. There are others out there though that should be an advantage over the std aluminum.
 

chris4x4

Seaman Apprentice
Joined
Dec 22, 2007
Messages
34
Re: Why an SS prop?

Wow! Thank you so much. I thought that the max rpm. was 6000. So, Im probably good with the prop I have. With only me and my wife in the boat, Im sure it would pull a little faster. Off the subject, What dictates the engines max. r.p.m.? Hope that isnt a stupid question. :)
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,648
Re: Why an SS prop?

Merry Christmas Kenny; been awhile.

On al vs ss I have proven the thin blade advantage. Other thing not mentioned by any responders in understanding the better performance (or what seems to be) is the fact that most alum props aren't cupped; haven't seen a SS that isn't. That's a big plus in reducing slip, ventilation, and an increase of apparent pitch.

Mark
 

BAYLINER185

Chief Petty Officer
Joined
Jul 30, 2007
Messages
474
Re: Why an SS prop?

I just bought a SS that isnt cupped to replace an aluminum that was :(

Also I screwd up and went with the same pitch BUT smaller diamater DAMN :(

My aluminum does 45 MPH on a 27 foot cruser the SS only did 35 WOT was a little higher with the SS but performance was CRAP!

My aluminum is a 15 3/8 diamater and the SS was a 14

That extra 1 3/8 is a HUGE differance. Im trying now to work this out with where I bought the prop, if not Ill ebay it and be happy with my Alum.

My point is like some of the other posts here is that simply going to an SS may not do you any good and maby a lot of bad. On my 18 foot bayliner I simply went to a SS prop of the same size and pitch ignoring the drop in pitch idea when going to SS and gained about 5 MPH. The boat went from 45 MPH to 55 at the rated RPM.

Doing that same thing on my cruser cursed me as I did go to a smaller prop size since I forgot I had a 15"er and dropped to a 14". I beleive thats whats killing me with this SS prop. I have to also remind my self this is NOT the same type of boat as my 18 footer and 45 on this big beast is DAMN good. Do I really need my cruser to go more that that? Not really. I think Im just going to stick to the Aluminum and forget about the BLING LOL........the boat is BLING enough no? lol
 

oops!

Supreme Mariner
Joined
Oct 18, 2007
Messages
12,932
Re: Why an SS prop?

hey chris. just re-read this post for the first time since i wrote the reply.

48 mph is very respectable!

oh And to QC


Not to beat you up ooops, but I want to clarify a few things


aww now yer makin me throw out evry thin i knowed bout stainlees steal,
and yer dern sendin me bak 2 skool !!!:D

allways enjoy the lesson, thank you
thanks for bein a saftey net for all my good advice:D:D

cheers
oops
 

roger3645

Petty Officer 1st Class
Joined
Aug 30, 2005
Messages
271
Re: Why an SS prop?

Chris how are you measuring your speed? Speedo or GPS?
 
Top