3 blade stainless vs four blade aluminum

[Randy stoner]

I have both for my 91 sunbird corsica 175 with a brand new 140 hp chev motor. The aluminum is very light and i know they can and will flex. The stainless of course is three times heavier. I know stainless gives you more bite due to its rigidity, however does that weight play into any detriment to the motor as far as power. Both 17 pitch.

randy

 

[ahicks]

I think the alum. prop flexing might be more of an issue if we were talking twice that amount of power (or more).

Unless you are talking about a pretty expensive stainless prop, I actually prefer the alum. for your application. Less concern about drive train damage from a prop strike, they never "rattle" on idle like some steel props do, and I feel better about going from forward to reverse and back without all the inertia/weight of the steel prop in play. That's me though... -Al

 

[Texasmark]

Stainless weight subject has been kicked around by big guns on here and my recollection is that it's a non issue from an engine wear and tear aspect. Yes I can see it being noisier with a sloppy fitting hub insert.

The 140 I/O is no speedster in the first place. Most aluminum standard production props have none of the finer amenities that most SS props possess: Rake, Cupping, variable pitch, thin blades and all. Other thing is, taking Solace Props for a reference as I just bought a new SS 4 blade and was entertained with their advertising of their different types of props, the 3 blade is designed for speed and high end running on lighter loads. The 4 blade is designed more for mid range cruising and pushing heavy loads without concentrating on max speed as a design criteria part of which is that designers recommend dropping 1" in pitch when changing from 3 to 4, everything else constant due to the inefficiency introduced by the 4th blade in the slip stream.

I think you have an apples and oranges comparison. With the weight of the 140 I/O at the transom, and the transom jump seats your boat probably has, and the love of folks to enjoy those seats....keeping them occupied, including during the "hole shot", and playing with water toys and hole shot with a skier and such, I'd opt for the Alum.

The other biggie here is the "dead rise" as shown in this picture I pulled up on the www: https://boats-from-usa.com/sites/default/files/boats/2014-06/27/1168/sunbird-corsica-198-13097.jpg Not necessarily your exact boat but it shows the high dead rise at the stern I am assuming that brand/model of boat has such as standard equipment.....dead rise at the stern is great for a soft ride but it comes at a cost....."stern lift" out of the hole and planing time suffers.....less planing surface effect for getting on plane which adds to your need to look more at the 4 blade for it's stern lifting attribute.
On SS rattle, blame that on the type of hub insert, not on the prop. Rubber pressed in hub SS props, like the Solace I just bought don't rattle....some of the newer brand name props have plastic/brass inserts advertised to fit better and not "rattle".

Just some of my impressions for what they are worth.

 

[ahicks]

Agree on all points - but the rattle. That rattle is occurring due to slop in the drive train, not a sloppy fit on the driveshaft. And you see it most often at a low idle, which can be kinda lumpy on some engines, or engines not in perfect tune.

Rattle doesn't hurt a thing. If you run into it though, it can be irritating..... especially if you don't know what's causing it. -Al

 

[Tail_Gunner]

Only if the prop comes to a very abrupt stop, something akin to hitting a rather large rock.

 

[Randy stoner]

The boat came originally with the 3 blade SS, however I had a four blade Aluminum. So the consensus is use the four blade aluminum?. As for stern lift, i have recently purchased Smart tabs and they are supposed to assist in stern lift to get on plane quicker. I guess its going to be trial and error for me. Last year I ran a high five 15P on it before the new motor and i got a solid 35 miles per hour with five of us in, so im hoping for a little fun this year as well with tubes and maybe even skis.

Thanks

randy

 

[Texasmark]

The boat came originally with the 3 blade SS, however I had a four blade Aluminum. So the consensus is use the four blade aluminum?. As for stern lift, i have recently purchased Smart tabs and they are supposed to assist in stern lift to get on plane quicker. I guess its going to be trial and error for me. Last year I ran a high five 15P on it before the new motor and i got a solid 35 miles per hour with five of us in, so im hoping for a little fun this year as well with tubes and maybe even skis.

Thanks

randy

You nailed. You can bla bla all day long but the "proof is in th pudding" (how does it taste). Only way you will really know is to run it. Yes the tabs are designed to deflect water down at the transom which helps to trim the boat out and stay on plane at a lower speed with lower HP required.

If you are going with the tabs, the SS 3 blade will probably be your best bet.

 

[skuhleman]

The boat came originally with the 3 blade SS, however I had a four blade Aluminum. So the consensus is use the four blade aluminum?. As for stern lift, i have recently purchased Smart tabs and they are supposed to assist in stern lift to get on plane quicker. I guess its going to be trial and error for me. Last year I ran a high five 15P on it before the new motor and i got a solid 35 miles per hour with five of us in, so im hoping for a little fun this year as well with tubes and maybe even skis.

Thanks

randy

I used to have a boat very similar to yours. Same engine outdrive also. I really played around with a bunch of different props. Mine liked a 17p for holeshot and a 19 for speed. Playing with aluminum props, I never could merge the 2. Switched to a high rake and cup stainless 19. I was able to get the 17 holeshot and the 19p top speed. But I tried a good 6-8 different props before finding the sweet spot.

 

[QBhoy]

Depending on the stainless 3 blade in question...normally as far as I’ve seen...the same pitch 4 blade ally will run more rpm and certainly less speed. Most recently on a 19ft regal with a 4.3 mpi. It had a 21” 4 blade spitfire ally. It ran to the limiter at 4950 rpm at about 47 mph from memory. We tried a 19” tempest plus 3 blade. That ran to just short of the limiter at 4900 rpm and about 52 mph. Despite the less pitch. Can be a guessing game completely !

 

[Tail_Gunner]

Depending on the stainless 3 blade in question...normally as far as I’ve seen...the same pitch 4 blade ally will run more rpm and certainly less speed. Most recently on a 19ft regal with a 4.3 mpi. It had a 21” 4 blade spitfire ally. It ran to the limiter at 4950 rpm at about 47 mph from memory. We tried a 19” tempest plus 3 blade. That ran to just short of the limiter at 4900 rpm and about 52 mph. Despite the less pitch. Can be a guessing game completely !

What I no longer see on this prop forum is the use of slip calculations. At one time that indeed was the benchmark for determining a props efficiency. That is too bad actually it did help clear up the air a smidge.

Looking back it became apparent one could attempt to squeeze the blood out of a prop/boat combo and yet in the end it became apparent one only spends about 10/15% of their time at WOT and 85% of their time at cruise or below.

The below tools can be quite interesting if used, transparency does come to mind...I love that word transparency...
Stickly a opinion your mileage may vary....and grammar lol..

Go-Fast.com > Knowledge base > Find your prop slip > Prop slip calculator

Read This First!!

ESSENTIAL DATA REQUIRED When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions. 1) Performance issue you are trying to correct. 2) Current prop...

forums.iboats.com

ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

 

[QBhoy]

What I no longer see on this prop forum is the use of slip calculations. At one time that indeed was the benchmark for determining a props efficiency. That is too bad actually it did help clear up the air a smidge.

Looking back it became apparent one could attempt to squeeze the blood out of a prop/boat combo and yet in the end it became apparent one only spends about 10/15% of their time at WOT and 85% of their time at cruise or below.

The below tools can be quite interesting if used, transparency does come to mind...I love that word transparency...
Stickly a opinion your mileage may vary....and grammar lol..

Go-Fast.com > Knowledge base > Find your prop slip > Prop slip calculator

Read This First!!

ESSENTIAL DATA REQUIRED When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions. 1) Performance issue you are trying to correct. 2) Current prop...

forums.iboats.com

ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

I’m a religious believer and even fascinated or obsessed with prop slip calculations. With my fast boat, I’ve had it down to 4%

 

[Texasmark]

I use them religiously especially on questions in the propeller section where somebody is looking to change and what to expect. I use the Go-fast.com Prop Slip Calculator. QBhoy, My 2002 Crestliner with it's aluminum hull and reverse chines, runs single digits also with it's normal load....me and gear. That picture you posted of your mil a month or so ago had to be in the area you mentioned.

 

[QBhoy]

I use them religiously especially on questions in the propeller section where somebody is looking to change and what to expect. I use the Go-fast.com Prop Slip Calculator. QBhoy, My 2002 Crestliner with it's aluminum hull and reverse chines, runs single digits also with it's normal load....me and gear. That picture you posted of your mil a month or so ago had to be in the area you mentioned.

Sounds nice texasmark. Yeah...at its best, it’s around 4%. When it’s up on the pad and aired out, it does very well to be fair. Heavy heavy boat for 18ft, but once she’s going...can’t think of many or any quicker 18ft boats...that have a windscreen, fancy seats and cupholders, haha. Special wee boat. Only know of about 4 of them for sure around the world. Apparently about 15 made back then, in performance edition spec.
Anyway. Bored you enough by now haha.