Need. More. Speed.

QC

QC

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Re: Need. More. Speed.

I actually like that plan :) Good luck!
 
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Circles47

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Re: Need. More. Speed.

pokman said:
In my opinion I would try a 19p ss and see where that puts you. I am no prop expert but I had a 94 125 2+2 on a 17ft rinker runabout. The weight of your boat and mine was probably similiar. I could run 41 with a 19p aluminum, and about 44 with a 21p aluminum. These are two different types of boats I know but I would think you should be able to see around 40.
Click to expand...

Pokman, was doing some re-reading and had a question for you. What kind of hole shot did you have with the 19 pitch? Could you pull someone up on skis?
 
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pokman

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Re: Need. More. Speed.

circles,

I had a great holeshot, I pulled up guys over 200 lbs pretty easily. Thats why I was suprised at your speed, I would have thought faster. If I was you I would at least try out a 19p ss if you could. You could always use your 17p aluminum as a backup or for pulling up a big skier. Another thing to think about is on my current boat when I went from a black max to same diameter and pitch vengeance ss, I actually gained 200 rpms which I figure is because of more efficiency. Again I know prop expert but I think good 19p ss wil get you to 40 mph. I will look up the dry weight of your boat and my rinker to see the weight difference.
 
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pokman

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Re: Need. More. Speed.

circles,
checked the weight yours was 1470, rinker was 1340. SO similiar, but yours is a deep-v, so I think 40-42 is possible, I just don't know how good a holeshot you'll have.
 
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Circles47

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Re: Need. More. Speed.

pokman said:
circles,
checked the weight yours was 1470, rinker was 1340. SO similiar, but yours is a deep-v, so I think 40-42 is possible, I just don't know how good a holeshot you'll have.
Click to expand...

Thanks Pokman, for the input! I'll let you know how it works out!
 
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Circles47

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Re: Need. More. Speed.

Just spoke with the guy where I ordered my new prop from, 13-1/4 x 17 S/S. He's telling me now that other than 1-2 mph increase, I can expect absolutely no benefit to a stainless prop over an aluminum prop. No performance increase, no handling increase, nothing...nada...zilch. Even though his "Prop Wizard" offers an increase of pitch to 19 for "cruising and performance" for my specific boat/motor, he says it will actually cause my boat to slow down several mph, due to 400 RPM loss. He said that if your current aluminum prop is close to max RPM's, increased performance from a stainless prop is only a dream. He also said that increased performance from aluminum to S/S is really only effectual in boats over 50 mph. If you want more anything....get a bigger motor. Is what he's telling me accurate???
 
QC

QC

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Re: Need. More. Speed.

I'd say he is consistent with what we typically have said around here. 1 -2 MPH is significant in our world ;)
 
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fishndirk

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Re: Need. More. Speed.

The 1-2 mph dfference is a reality that I have seen many times. True, this is not much. But there is something else he was forgetting about. To say that there would be no performance difference at all is a false statement. The molecular structure of steel is much stronger than aluminum. This is a fact that cannot be argued. Because of this they can make the blades of ss props thinner and more hydrodynamic than "most" al props. Thinner blades means less water resistance and therefore less power required to move them at the same speed. Less power required means less fuel burn and therefore less throttle to keep your boat on plane.
 
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fishndirk

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Re: Need. More. Speed.

That is a good tool on that link. The numbers I posted on the first page of this post are exactly what they use to calculate those numbers. It does work too. The figures I get for my boat out of it are exactly what shows on gps on the water. The only key is having the correct data to go into it.
 
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fishndirk

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Re: Need. More. Speed.

That's good, I do like that one better. I like the description at the top of the page too
 
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Circles47

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Re: Need. More. Speed.

Ok, after speaking this morning to a man from the place I bought the prop from, and enduring all his negativity regarding the prop I had ordered, UPS brought it a little later. It was kinda hard to get excited about it tho. I wondered, with so little benefit, should I just send it back while I still can? But I finally decided that 1-2 mph was better than nothing, and I still wasn't sure I really agreed with all he was saying. (It's a wonder he even sells S/S props to anyone!) So, I put the prop on, and headed to the lake for some real numbers.

I was very pleasantly surprised.

Hole shot is every bit as good as before, if not better.
Boat comes up on plane very fast....faster than before.
RPM's are exactly the same as before....5200 at WOT.
Speed as per GPS increased from 34-35 before, to 38-39 now. :D

I entered this data in the 2 prop calc programs above, and am showing a prop slip of 5-6% down from 16%? Seems like too little for a deep vee, but I'll take it! The new S/S prop definitely has more cupping to it, perhaps that's where some of the prop slip decrease comes from.

Also, at WOT before, I would get some motor bounce, so I rarely ran at WOT. Now...no motor bounce whatsoever.

All in all...I'm extremely satisfied with the performance of the new prop. And.....still left wondering what a 19 pitch would have really done!:)

Thanks to all of you who had a part in my "Prop education"!
 
BonairII

BonairII

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Re: Need. More. Speed.

Out of curiosity, could the OP's boat be a tad heavy(wet flotation foam etc) and losing speed because of it?
 
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fishndirk

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Re: Need. More. Speed.

Outstanding, I'm glad it worked out for you. People hold a grudge against certain things because of stuff they were "told", but the numbers don't lie. When someone gets all emotional about stuff like that itsusually because they've formed an opinion about it and its easier for them to downplay or argue it rather than change their thought process on it. I'm still arguing with a friend of mine who hung up on me on the phone last week because he swears the number of the prop pitch represents degrees, not inches. But once again, the numbers don't lie. Sounds like you got a good rig now.
 
QC

QC

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Re: Need. More. Speed.

BonairII said:
Out of curiosity, could the OP's boat be a tad heavy(wet flotation foam etc) and losing speed because of it?
Click to expand...
Not with 5% slip it isn't ;) That number does seem too low, but cupping can be it. Great result!!!
 
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pokman

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Re: Need. More. Speed.

glad it worked out. Still think you would run over 40mph with a 19p though:D
 
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Circles47

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Re: Need. More. Speed.

pokman said:
glad it worked out. Still think you would run over 40mph with a 19p though:D
Click to expand...

I agree pokman. I'd like to find someone who has one and try it out first. The guy who sold the 17 to me said that a 19 would drop my speed below the 17.... I think he's full of beans! :rolleyes:
 
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