New prop on and tested...results???

Prop guy finally got the hub right so I got to put on new prop and test. Here's the info:

Everglades 200cc (Flatbottom; w/ tunnel 24" wide x 3.5" deep) No jack plate
2005 Yamaha 115 four stroke
2800 lbs (boat, motor, gear, me, passenger, gas, etc)
New prop: Power Tech SS PFS4 (4 blade cupped) 13x15
Max WOT RPMs full throttle: 6000 (didn't want to try for more, but felt I could get them)
Max speed at WOT 6000: 26.5 knots (GPS)
Speed at 4500: 21 knots (GPS)

Old Prop: 13 x 19 Aluminum (don't know make)
Max RPMs full throttle: 5200
Max speed at WOT 5200: 30.5 knots (GPS)
Speed at 4500: 25 knots (GPS)

Questions: With new prop, what should I peg as my max WOT rpm? What should I cruise at? What is fuel use at each of these rpms? My Yam owner's manual says "max PRM range: 5000-6000". What should that tell me for my set-up?

Basically, I like this new prop because it has dramatically improved my hole shot, but I don't know how to run it at optimum performance. Lots of questions so thanks in advance for your help!

Re: New prop on and tested...results???

The new prop obviously has a lot of slip. It'll never be as efficicent as one without that much slip that still gets you to 6000.

Re: New prop on and tested...results???

Is there a way for the prop shop to modify this prop to minimize that slip? Also, did you determine the slip by studying the RPMs (as opposed to the speed)?

Finally, what in your opinion is the best RPM at which to operate this set-up as it is? Meaning, best for fuel, motor longevity, performance, etc.

Thanks

Re: New prop on and tested...results???

I ran my prop calculator with the boat and motor info I have. Please Check all my information on RPM, gear Ratio and Boat weight because if they are wrong everything I say below will be WRONG as well. My program shows you need a 16" prop and it should turn about 5,900 RPM. I also show a different weight than you stated as I show that boat to have a base weight of 2,150 pounds. If I am wrong on this let me know please, because it will change the numbers some, at 2,800 pounds you need a 17" pitch, but at 3,500 pounds you need a 16" Pitch.

Boat and Motor Info



Prop Picker





South, there is something major wrong with that PFS4 prop you bought. Powertech says it is a 4 blade Triple cup flats prop, and it acts just like your old aluminum prop that has been reduced to a 15" pitch. Just by changing to a 4 blade prop you should have lost some RPM theoretically, and everbodies idea of cup is different, but a TRIPLE cup prop should act at least like a 17" theoretical pitch prop and eat some RPM and help reduce prop Slip. Your new prop has the same RPM just like any 15" Pitch aluminum prop would have, and that is certainly not the way it is supposed to be.
I ran the numbers for you and here are my results:

If you had just bought an aluminum prop of the same make and model you already had on your boat but just bought a 15" pitch instead of the 19" pitch you had your RPM would have increased from 5,200 to 6,167 RPM, and that appears to be what you can turn now with your statement about you felt you could get more RPM. Personally I think they gave you the WRONG prop, because it certainly is not living up to it's claims of "reduce pitch 3-4 inches, triple cup. 75-130 H.P."

Prop Change




Prop Slip did not get reduced anywhere near what it should have with a Triple Cup as well. And you actually INCREASED your prop Slip at WOT.

Prop Slip




In my opinion you need to check if that is the prop you paid for, beause I don't even get close to believing it is, not with these numbers of speed and prop slip. You could have purchased a cheap aluminum prop and be able to get the same RPM and prop slip from it. I am not denigrating your prop, but I am telling you that you did not get the correct prop for your use, nor is it the one that you paid for, in my opinion. And your Hole Shot would have increased dramatically just by changing to an aluminum 15" prop as well.

H

Re: New prop on and tested...results???

First off, thank you very much for all of the info...

I looked over the info you entered for engine, only thing I saw was engine is a 4 cyl, you have listed 6 cyl (I triple-checked Yamaha website for this).

Triple-checked rpm range--what you list is what is listed on yamaha website.

Boat weight--this is a good question. Everglades doesn't have its specs listed on website anymore as its a discontinued model. I asked them for boat specs, they sent me a "trailer king" spec sheet for measurements; it listed boat hull as weighing 1800lbs. I've seen it listed as 2200lbs on a sales sheet from an individual; I'd be curious to hear where you found your info. I can't find these specs anywhere online.

As to the prop itself, I bought it off an individual; the stamp is still (mostly) visible; it is a 4 blade stainless 13" dia prop; the pitch number had worn off but prop guy used tool to measure it; he also confirmed it's a powertech 13" diam. I had to deduce it is a PFS4 because that is the only one that comes in 13" diameter.

The old prop rpms were measured at full throttle, is it possible that the throttle has been adjusted to ensure that previous owner never went over 5200 rpm (that there is still some rpm left in engine)? I ask because I have heard of people doing this; don't know if he did.

IF ONE OF THE BLADES WAS SLIGHTLY BENT, COULD THIS BE THE ROOT OF ALL THE PROBLEMS????

Lastly, the seller has already said I can return it to him if it doesn't work out. Should I eat the money I spent rehubbing it and start over?

What prop would you recommend for this set-up, keeping in mind hole shot is more important to me than top-end, although I'd rather not lose 20% or more on top-end? Is there a happy median?

And, if I go back to my 19 pitch, what is best cruising rpm for long runs and what kind of gph can I expect from burn from it?

Thanks again for all of this info....

Re: New prop on and tested...results???

South a bent blade can do anything, it is NOT predictable. But it is not a PFS4 in my opinion. A bent blade has to be fixed as it can ruin bearings in the lower end and is not good for the motor.
If you didn't pay much for the prop I would give it back and buy a 16" pitch Turning point aluminum prop at this site as it is cheap and has a lot of very good characteristics for most boats.
Check the butterfly in the carburetor to make sure it is parallel at wide open throttle. If it is, it is fine.
The 19" is lugging your motor BAD, buy the 16" to get your RPM close to maximum RPM. The 16" will give you a great hole shot and should turn about 6,000 RPM.

Please send me the new speeds and RPM so I can enter them into my database.
H

Re: New prop on and tested...results???

As far as your best cruising speed that will take making a few runs at various cruising speeds and keep close track of fuel use.The best practical cruising speed can be anywhere from just on plane to about 2,000 rpm higher.
Any motor will use about 10% of the rated hp in gph.at wot.
about 11.5 gph in your case.

Re: New prop on and tested...results???

I went out and retested more scientifically. I derived these numbers on the same stretch of water, always driving south, at several different speeds with both props, then used a prop slip calculator on-line and here's what I found (NOTE: mph from GPS). However, I don't know what these results indicate:

3 blade 13x19

Gear ratio pitch RPM Theoretical Speed Actual Speed (mph) Slip(%)
2.15 19 5200 44 36 18
2.15 19 5000 42 33.5 20
2.15 19 4500 38 30 21
2.15 19 3500 29 20 28

4 blade 13x15

I've tried to run these numbers, but they don't seem to be coming out correctly, unless my slip is only 5% for all speeds, can't seem to be right.

RPM Actual Speed (mph)
3500 16.68
4500 24.7
5000 27.6
5500 30
6000 33

Can you guys tell me what these new numbers mean?

Re: New prop on and tested...results???

South you tried to do an excellent job, the only error you made was not getting the speeds from 180 degrees apart from each other. When you make two runs back to back and add them together then divide by two you take any currents into effect and null them out and it gives us a true GPS speed of that prop.
But, you did give us a direct comparison between the two props no matter what current was or was not there, so that is great. I enjoy working with people who take the time to try and do it right, and you tried very hard.

I ran the numbers through my program and came up with the results that I will post below. I am assuming again that you didn't try to go over 6,000 RPM with the 15" prop, just as you did before. If you changed to a 16" Pitch 4 blade in the same model and the same diameter as the 15" Pitch I show you would increase your WOT speed by a couple of miles per hour if it attained the full 6,000 RPM, but it might not be able to do that. It appears to me that a larger diameter prop would decrease your Prop Slip, but it would also decrease your RPM and that very easily could become a washout because RPM loss would also decrease your speed as well. There is another reason that you could be showing such a high slip for the 15", but it really doesn't matter. I would like you to run the boat for at least 30 seconds at Wide Open throttle one time though, just to see what the Top RPM are.

In my opinion if the 15" pitch prop you have now does not have a bent blade, which the prop shop can tell you in a heartbeat by trying to balance it, I would use that prop as my Primary prop and keep the 19" on the boat as a backup in case something happens to the 15". I think it would be a crapshoot to try and find a better alternative prop.

As far as cruising speed is conerned I would try at about 4,750 RPM and 28 MPH, without a Fuel Flow meter you never know but I think that is a good cruising RPM considering you can probably turn the prop about 6,100 RPM if you decided to.



H

Re: New prop on and tested...results???

HS,

thank you very much for your info. I am going to keep it and run it for awhile. If I'm not happy, I'll keep it as a spare, and get back to the drawing board.

One more question in extension--what kind of difference in performance from this prop can I expect from the addition of a bob's jackplate w 6" setback?

Re: New prop on and tested...results???

With that prop all you will do is be able to turn more RPM above Recommended WOT, and that would not be good.

H

Re: New prop on and tested...results???

H, you weren't kidding. I can turn more RPM than ever before. I really have to keep an eye on my tach when running w/ engine up. Lost some speed too, because rpm have increased so much.

Am I ok to keep this prop as long as I keep an eye on rpm, or do I now need to move another prop (keeping in mind speed is secondary in importance to hole shot)?

Re: New prop on and tested...results???

If it was me I would bring it to a RELIABLE prop shop and ask them to cup the trailing edge enough to add 1" to 1.5" of theoretical pitch to the 15" 4 blade prop. This will do two things for you, it will add a little more top end speed and control the water better off the back of the prop which will let you raise the prop higher without ventilating as much as it does now which will help with prop slip and speed but still give you a great hole shot. Bus ask the guy first if the normal pitch of that prop is a 13" Pitch before he does anything and not including any cup already in the prop, if that is true do nothing and get back with me.

H

Re: New prop on and tested...results???

Perfect, thanks. After my problems with the last prop shop, I'll be finding a new one here to look at it. Since you mentioned it, I do remember him saying that "with the cup, it was 15" pitch", which tells me the cupping might be after market and make it 15, as opposed to it being a factory 15? As you'll recall, the factory stamp pitch number wasn't legible. It said "13x1 ".

What is the significance of this in regards to the things you and I have already tested?

Re: New prop on and tested...results???

It changes everything LOL. It isssss the PFS4, butttt it is a TRUE 13" Pitch PFS4 that is ACTING theoretically like a 15" Pitch prop. That was the whole problem all along, you said it was a 15" Pitch PFS4 and that means it should have acted theoretically like a 17" pitch prop, which it didn't. That is why it is exceeding the RPM it should be getting and that is why it acts like a 15" pitch aluminum. And that is why I said it wasn't a PFS4.
You have a dilemma now, you can accept having to watch your tach all the time for over revving or you can buy a TRUE 15" PFS4 and when you lift the motor on the jackplate you will find that you will gain more speed and the tach will move up closer to the recommended WOT. I would expect your speed to move up to about 36 MPH or more and your prop slip to go down some. Your hole shot should be close to the same but just a little bit slower than it is now. Sorry, I just didn't know it was a true 13" PFS4. You can sell the 13" PFS4 you have now on craigslist or ebay possibly.

H

Re: New prop on and tested...results???

OK, I understand. Exactly what do I need to ask the next prop guy when he examines it? Ask him what the "true pitch" is? To dumb it down, ask him what that missing number on the prop was? I guess that would have been the true pitch?

Re: New prop on and tested...results???

Ask him the TRUE pitch of the blade with no theoretical cup pitch added to it.

H

Re: New prop on and tested...results???

Got it, thanks again. I'll get back to you after I've had it looked at.

Re: New prop on and tested...results???

Sounds great.

H