Prop tuning gurus

[jerseysportfisher]

Gentlemen,

here it goes, i have a 28ft master marine center console, 1991 yammi 250 salt. Boat is very heavy with very sharp entry points, its no speed demon by any means. I have been trying to tune for maximum perf/fuel consumption and have been left dumbfounded.

first setup is the original
ss factory yam prop 15x17

cruise @ 4200 25.5 26 knots wide open @ 5000 35.5 normal chop 37.5 on the glass

second setup solas 14.4x19

total crap ...... completely useless

third setup

turning point 15x15

cruise @ 4200 18 knots wot @ 5400 23.5 knots

fourth setup

solas 16x13 cruise @ 4200 22.5 knots wot @ 5100 26 knots


is there any more performance i can widdle out other than using a factory ss prop or just give up and live with it ?

all other props are aluminum
thanks

 

[junior1113]

Re: Prop tuning gurus

id look for 15p ss yam factory #'s were good on that 17 just not enough wot rpm that 17 can be repitched lower by prop shop

 

[MikDee]

Re: Prop tuning gurus

Apparently, your bending props! Does the word aluminum ring a bell?
Just kidding, but knowing your horsepower, and guessing the boat weight (Heavy) using the little common sense I have My theory is the aluminum props are flexing too much to do you any good It might be different if you had twins, but it just sounds like too much load for one aluminum prop

What are you trying to achieve, is your motor below the Max rpm? If so what is the Max recommended rpm, so we can help you? In any case, please buy a SS prop,,,lol

 

[hwsiii]

Re: Prop tuning gurus

Jersey, if these are GPS speeds I would be surprised, as I show you with a 3% Prop Slip on the Yamaha 15 X 17, I presume that is their Painted Steel semi cleaver prop. The Turning Point shows a Prop Slip of 36% at 4,200 AND 5,400 RPM and that doesn't make sense, and the Solas shows a Prop Slip of 9% at 4,200 RPM and 14% at 5,100 RPM and I usually never see an increase in prop slip on a planing hull at WOT RPM. I believe the numbers you are giving us are not exactly the numbers that the boat attained, possibly you just remembered wrong, as I do regularly. I am NOT attacking you, just trying to figure this out and help in any way I can.
I would very much like to know the base weight of your boat, degree of deadrise, how many people and extra weight you carried on these test runs, and did you run them the same day and did you run in one direction and then turn 180 degrees and run in the other direction then add the two numbers together and divide by two for each prop test to negate the possibility of currents affecting the test results.
I show your motor to have a 1.81:1 gear ratio and recommended WOT RPM to be 4,500 to 5,500 RPM, if these numbers are right I ran some figures and they are below, I also show that if you changed to the 15" pitch in the Yamaha prop you will gain about 500 RPM which will put you right at the MAX rated WOT and probably lose about 1 MPH at top end. BUT if that Yamaha 17" Pitch really has a prop slip of 3% I can't imagine that the 15" pitch will do the same. THe only time I have seen prop slip like that was with a Yamaha Performance series prop that couldn't turn but 5,050 RPM and WOT should have been 6,000 RPM.

Here are your Prop Slip Numbers

Prop Change

While I am at it, I will also state that the blade flex most people talk about with aluminum props at speeds lower than at least 45 MPH is not a viable statement in my opinion, if it was then aluminum props would attain more Prop Slip as the speed and RPM increased because of the water pressure exerted on the blades at these speeds in a boat, and in fact that is NOT the case if you will study the prop slips of most boats with aluminum props. Because as the speed increases you will notice that the Prop Slip decreases all the way to WOT RPM, and if aluminum prop flex was true you would see Prop Slip go UP as the RPM went up not DOWN. The MAIN difference in aluminum and stainless steel props is in thinner blade thickness because of the difference in material strengths, which makes for less disturbance in the water flow between blades as they turn with stainless props, as the stainless blades are much thinner. And the MAJOR difference is in blade GEOMETRY of propellers built in stainless steel that is NOT incorporated into most aluminum propellers. The only props I know of in aluminum that have a LOT of blade geometry changes in them is the Turning Point Props and they certainly act more like stainless props than aluminum props.
There is a lot of talk here about the differences in stainless and aluminum propellers, but there is not enough talk about blade geometry other than the amount of rake that either increases bow lift or zero rake that is used for stern lifting. There is some talk about cupping as used for theoretical increases in pitch and for increasing stern lift, but hardly anything is ever mentioned about progressive pitch and rake and cupping at the prop tip to increase the rake and dynamic thrust.

H

 

[jerseysportfisher]

Re: Prop tuning gurus

hwsiii, i have to agree with some of your statements. I mic'd the aluminum props, there's no way i putting out that type of horsepower to flex thoose blades that much where it will hinder performance. All theese numbers were aquired through gps and speedo (both are dialed in together, in case gps were to take a crap). I believe my conclusion for the performance results lies in ear design and cup. The yamaha prop is not painted, it's not shinny anymore either. Also which you can not wrap you brain around also because you can not physically see it is the hull design, this also plays a big part in this. it is not like a typical mako/sea ray/ regal. It is long and narrow, very similar to a WWII destroyer

the best pics i could find for you on short notice

http://www.iboats.com/cgi-bin/marine_classifieds/view_photos.cgi?ad_id=501367&img=

http://www.randrcharters.com/index.php?page=boats

http://www.boat-world.com/disppic.php?ID=896402966&picno=2

http://www.oceanlist.com/boat-for-sale-1981-MASTER-MARINE-INC-True-World-Center-Console-16427


allthough theese shots really do no justice to the bow and deadrise

 

[jerseysportfisher]

Re: Prop tuning gurus

FYI

the surface area on the 16x13 in nearly 2.5 that of the yamaha

the surface area on the 15x15 is roughly 1.87 that of the yamaha

i have no accurate way to measure cup but i can tell you the factory ss prop is quite agressive compared to the rest.

all tests were the same day, no wind 1 person in the boat. boat was trimmed out with tabs.

weight approx 5500 dry

from what i have found bow entry is between 68/72' deadrise 20-24'

8'6 beam lenght with outboard 30 hull 28.6

 

[MikDee]

Re: Prop tuning gurus

Well it seems all of your props, except the last Solas 16"X13" were too small in diameter for the weight of your boat IMO, I had to put at least a 15" Diameter 17" pitch Michigan wheel on my old 24' SeaRay Cuddy with a 260 Mercruiser, so it wouldn't fall off plane at times, especially at every turn That boat would do 40mph and was always run with a light load, engine tweaked, 2 people or less, and always the minimum amount of fuel :redface:

So, It appears that you don't consider aluminum to flex, but you haven't had much luck with them, so why do you keep buying them

 

[jerseysportfisher]

Re: Prop tuning gurus

flex to the point were the ear looses its shape. Its more likely to get cavitation then bend/flex an ear.

anyways, the reason i keep buying them is it is not cost effective to buy 3-4 ss props @ 430 a piece to tune the boat. Local guy buy me wants 3g to tune the boat, thats all he does. I have no problem generalizing pitch and diameter @ 75-80 a prop, then go by a similar SS.

 

[rrhodes]

Re: Prop tuning gurus

I would find a different Prop guy. Check boat dealers in your area too. Many of them will let you swap props until you get the one you need. I think Mercury has a prop swap program as well.

 

[Tail_Gunner]

Re: Prop tuning gurus

hwsiii, i have to agree with some of your statements. I mic'd the aluminum props, there's no way i putting out that type of horsepower to flex thoose blades that much where it will hinder performance. All theese numbers were aquired through gps and speedo (both are dialed in together, in case gps were to take a crap). I believe my conclusion for the performance results lies in ear design and cup. The yamaha prop is not painted, it's not shinny anymore either. Also which you can not wrap you brain around also because you can not physically see it is the hull design, this also plays a big part in this. it is not like a typical mako/sea ray/ regal. It is long and narrow, very similar to a WWII destroyer

the best pics i could find for you on short notice

http://www.iboats.com/cgi-bin/marine_classifieds/view_photos.cgi?ad_id=501367&img=

http://www.randrcharters.com/index.php?page=boats

http://www.boat-world.com/disppic.php?ID=896402966&picno=2

http://www.oceanlist.com/boat-for-sale-1981-MASTER-MARINE-INC-True-World-Center-Console-16427


allthough theese shots really do no justice to the bow and deadrise

Nice boat....and yes the boat is deforming the alum prop..err the motor that is...

(is there any more performance i can widdle out other than using a factory ss prop or just give up and live with it ?)

Youve pretty much summuned it up right there. Or any ss that is suited to your application

 

[hwsiii]

Re: Prop tuning gurus

Jersey, this Yamaha stainless prop is very intriguing. Is there a possibility you could take about 4 pictures of that prop for me. I would also love to have the factory part number for that prop as well. The differences in blade surface areas is also very significant and could be part of the reason for the significant differences in Prop Slip and Speed.

I actually called Yamaha in the states about their Painted Stainless and their Performance series props and John at their technical support could give me no information on the differences between the mean width ratios or blade surface area between the props, so I ended up calling the office in Japan and they told me it was PROPRIETARY, and I told them that ANY prop shop could tell anyone the differences between the two and how was that Proprietary.

I do not believe that you can do any better than what you have with the Yamaha stainless now unless you changed to the 15" Pitch in the same model, and I am not positive about that. But if you can borrow one I sure would try it to get the RPM up to maximum, it should increase your hole shot and time to plane.

H

 

[Tail_Gunner]

Re: Prop tuning gurus

• Manufacturer: Yamaha
• Horsepower: 250 HP
• Years: 1990 & Newer

• Model: 250 HP
• Maximum RPM Range: 4500-5500 RPM
• Propeller Pitch: 15?

http://boatpropellers.iboats.com/Ya...23373/?**********=769361145&*******=665459456


http://boatpropellers.iboats.com/Ya...11204/?**********=769361145&*******=665459456


http://boatpropellers.iboats.com/Ya...17770/?**********=769361145&*******=665459456

17@5000
16@5200
15@5400
14@5600


You have a lot of choices..Id go up into the outboard forums and find the sweet spot for that yamha..that is its peak operating rpm...Yamaha has nothing special going on with there SS props..They buy from someone...

 

[hwsiii]

Re: Prop tuning gurus

Tailgunner, Yamaha actually owns their own propeller company. Precision Propellers, the maker of Stiletto and Turbo brands, is part of their umbrella of corporations.

H

 

[Tail_Gunner]

Re: Prop tuning gurus

And as old Paul Harvey stated so many times Now you know the rest of the story....

Now as to alum not deforming..plz explain.......

 

[jerseysportfisher]

Re: Prop tuning gurus

TG, actually my sweet spot is 4200 in this particular engine\boat combo. Thats my ideal cruise where i'm not pouring fuel down the carbs, and doing a relatively good speed. I am kicking around using a 4 blade, and now working with the gentlemen at propgods, where we are looking at other reasons. as for the aluminum, yes i agree aluminum has a yield lower then stainless, its also has elastic properties, although the paint or powder coating on the aluminum does not meet the same elastic properties. There for if it was flexing as much as some people think i would see minute stress fractures in the coating. Now with that being said, the most strain on a prop is during the hole shot, for theory lets say due to flexing of the blades I lost maximum 1-1.5 inch of pitch . That would actually increase my holeshot performance, as the boat planes out load is taken of the prop and it is back to where it should be. That is why I feel blade design and cup and rake play a bigger part in my results then flex.

 

[hwsiii]

Re: Prop tuning gurus

Jersey, I have discussed props with Ken before, and i think he is Excellent at his profession, and if you were close to him he would bring you 3 or 4 props and let you do water tests with him there to help explain what is happening and make sure you get the right prop. He is very helpful with his prop guidance and only charges a small exchange fee for props and for his help and expertise choosing the right prop.
If your gear ratio is the 1.81:1 as I have found, these are my postulations. I do believe in this case that a 4 blade prop will lose a lot of RPM at WOT, because like you said before about the differences between blade surface areas, but I don't see where you have anything to lose unless Ken can't get you the Yamaha 15" Pitch because he does exchange props I believe at a cost of only $ 35 for each exchange. There is a difference of 13 MPH between the 4 blade Solas and the Yamaha stainless and yet only a 100 RPM difference. With a 4" change in Pitch you should have gained about 1,200 to 1,300 RPM in the same model of Yamaha prop you are running now, but with the increased surface area and 4th blade and different blade geometry you only gained 100 RPM. The Solas was also aluminum which increased the thickness of the blades and created a lot more disturbance between the blades, especially with the 4th blade added. Don't get me wrong there is a major difference between the Solas 4 blades and the Powertech OFS4, but the blade surface area still increases dramatically and at your WOT setting I believe the blade surface area will lower your potential RPM very much, and there is NO way it can attain the 3% prop slip you are getting now.
After having said all this I believe you ought to try the OFS4, because I could be wrong and Ken is excellent at his profession and has a tremendous amount of Knowledge and years of Experience in boats and propellers, and will do everything possible to prop your boat correctly.
Tail_Gunner, the plastic deformation of an aluminum prop is there, but it is so minor that it plays no part in the actual performance of the propellers at speeds below about 45 MPH. There is a reason that aluminum props are much thicker than their stainless counterparts, and that is because of the differences in material strengths and by increasing the thickness of the blades in aluminum propellers they are trying to take into account those differences. Most aluminum prop manufacturers build their props with Aluminum Alloy 514 but Mercury makes their props out of Mercalloy, a product they invented that has 19 times more Silicone and 28 times less Magnesium in them, which increases their impact resistance when hitting an object.
When using aluminum the thicker blades create a lot more water disturbance between the blades as they turn and thus raise the prop slip over stainless props to a certain degree, BUT 95% of the difference between aluminum props and stainless steel props is BLADE GEOMETRY, not the elasticity of aluminum or its deformation from bending, just as there are such big differences in performance between a stainless steel prop with progressive rake and one with zero rake that are used on the same boat.
I still stand by my statement that blade flex in aluminum propellers in most boats does NOT cause prop slip to increase to a noticeable or quantifiable degree in speeds below 45 MPH ,and is not a viable statement.
If this were true then we should see Prop Slip go up as speed increases, NOT Down.
If anybody has any relevant data supporting the theory that aluminum prop flex does cause excessive prop slip please post it. Tail_Gunner, I would love to see you post the information you have that justifies the aluminum prop flex you are talking about. I would like to have everybody on this forum understand that BLADE GEOMETRY and not aluminum props is the major culprit in performance issues and PROP SLIP percentages.

H

 

[Tail_Gunner]

Re: Prop tuning gurus

Try to think of alum as Deforming...not big bend's but overall deformation...Prop's do have a design and when that design is Deformed it is not as effective there not biting the water

___________________________________________________________________

"BLADE GEOMETRY and not aluminum props is the major culprit inperformance issues and PROP SLIP percentages. "
_____________________________________________________________________________


Agreed but it deform's its just as simple as that ...There would be no need for the material called SS if not..


Designer's know this going into there design process and when using alum they will not build in a complex design or heavy cupping aka you will not find to many high rake alum prop's and Hustler is one of the only alum mfg's that advertise high performance cupping....and some of there results in this forum have been fairly eratic.

In your situation setback and motor height seem to be more of a fundamental of performance..."creating a balance point" than most anything else. If you were to go over to the Hull Truth you will find volumes of info on the subject and they generally end up prefering mercury props.....Mirage's or Vensura's Rev 4 etc.

 

[hwsiii]

Re: Prop tuning gurus

I didn't say it wouldn't flex, I said the flex is so inconsequential, it does not affect the performance of the prop under 45 MPH. I asked you to provide data that supports the contention that aluminum blades flex enough to cause a change in the pitch or prop slip percentage goes up as more load is put on the prop. My data shows that as the RPM goes up to WOT under 45 MPH Prop SLIP actually decreases, and that proves my point. Where is your proof that it causes enough deformation to affect performance and increases PROP SLIP. And your statement that "Agreed but it deform's its just as simple as that ...There would be no need for the material called SS if not.." proves nothing about aluminum deformation, it is INCONSEQUENTIAL it is SO SMALL.
When informed people on here talk about the differences between aluminum propellers and stainless steel, the discussion should be based on PROP GEOMETRY NOT any supposed blade flex in aluminum, as it is inconsequential.

H

 

[Tail_Gunner]

Re: Prop tuning gurus

I didn't say it wouldn't flex, I said the flex is so inconsequential, it does not affect the performance of the prop under 45 MPH. I asked you to provide data that supports the contention that aluminum blades flex enough to cause a change in the pitch or prop slip percentage goes up as more load is put on the prop. My data shows that as the RPM goes up to WOT under 45 MPH Prop SLIP actually decreases, and that proves my point. Where is your proof that it causes enough deformation to affect performance and increases PROP SLIP. And your statement that "Agreed but it deform's its just as simple as that ...There would be no need for the material called SS if not.." proves nothing about aluminum deformation, it is INCONSEQUENTIAL it is SO SMALL.

H

My data shows that as the RPM goes up to WOT under 45 MPH Prop SLIP actually decreases, and that proves my point. Where is your proof that it causes ..


Hmm and less wetted surface is in your data???Or do you believe hull drag in linear....There are just to many variable's to measure in absolute terms...But i agree in blade geometry...That is why alum props are basic in design..and very good value's at that..

 

[hwsiii]

Re: Prop tuning gurus

Well, if that is true then why did you blame it on aluminum PROP FLEX.

H