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Adding cup

1049 Views 33 Replies 16 Participants Last post by  ianwilson
Running a PowerTech PTR4 18p on my new Cayo 180 with a 90 SHO. Hull has 10 deg deadrise and small running pad.
Prop performs really well but think I would like a bit more grip in turns. With 2 guys and light fuel I can hit 48 mph right on the pins at 6100 rpm. At 30ish mph I can cavitate the prop if trimmed a bit. According to PT, I could definitely spin a pitch or 2 higher.

I read adding cup equates to 300-400 rpms which seems like the same as a move up to a 19p, but would it give me better grip and what speed changes should I expect? Also, I've never owned a Skiff with a pad, but I see the "trimmed out, riding on the pad" pics...should I be considering something different in a prop?

So, add cup, move up to a 19p, sell it or just leave well enough alone?
I know this is really sweating the small stuff, but it’s fun Haha.
What say our experts?
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· Zephyr Cove is on FIRE!
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Your custom prop guy will know what you need. Also, don’t rule out a three blade. As you may have read, I am a huge believer in three blade props for hole shot despite the internet myth that 4 blades are for hole shot and 3 blades are for speed. There are way more factors involved than just blade count, pitch and cup.
 

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Skipps propeller in North Charleston can get you dialed in, but be prepared to bring him the data. I went down a similar rabbit hole a few years ago and ended up with a Mercury Laser II on my Zuke 90. Went to Skipps to have an inch of pitch added due to slight over reving, but he convinced me to just add a little cup instead based on my running numbers. Sure enough that did the trick. In my case, I gained a couple mph because the motor could be trimmed out more at speed without blowing out.
 

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2007 Gordon Waterman 18
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Your custom prop guy will know what you need. Also, don’t rule out a three blade. As you may have read, I am a huge believer in three blade props for hole shot despite the internet myth that 4 blades are for hole shot and 3 blades are for speed. There are way more factors involved than just blade count, pitch and cup.
Tell us more about this as it does seem I get much better hole shot with my 4 blade than I do with my 3 blade.
 

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Discussion Starter · #5 ·
I’m close with the 4 blade, but that green Snake Bight with 90 SHO hits 53 and runs 50 loaded down with a PT 13.5x22 3 blade, don’t know which one but guessing PTR. It’s got me wanting to throw a big 3 blade on there 😂
Your custom prop guy will know what you need. Also, don’t rule out a three blade. As you may have read, I am a huge believer in three blade props for hole shot despite the internet myth that 4 blades are for hole shot and 3 blades are for speed. There are way more factors involved than just blade count, pitch and cup.
@ReelFisher thanks man I’ll give Skip a shout
 

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Tell us more about this as it does seem I get much better hole shot with my 4 blade than I do with my 3 blade.
It depends on the blade shape and cupping added. This is not a blanket statement but out of 45 skiffs I have rigged out for hole shot and shallow performance zero have a custom 4 blade, they are all 3 blade Foremans or Baumanns. Some of the shallow water Powertech shelf props are Foreman’s design.
 

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It depends on the blade shape and cupping added. This is not a blanket statement but out of 45 skiffs I have rigged out for hole shot and shallow performance zero have a custom 4 blade, they are all 3 blade Foremans or Baumanns. Some of the shallow water Powertech shelf props are Foreman’s design.
My PT 4 blade isn't close to the Foreman three in grip.
 

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I believe the impression that 4 blades are for holeshot came about because most people drop an inch or two of pitch when going to a 4 blade. Sure, it should pull harder on the low end...... it's like having lower gears in the rear end of a car. All things being equal, a 3 blade should spin up quicker. It's less rotating mass. Heck, a 2 blade would beat both of them..... but balance would be an issue.

Go to any ODBA race and walk the pits. Most every boat there will have a 3 blade on it. Vast majority are probably old Yamaha drags, or some close copy thereof.

Don't get me wrong. 4 blade has its place. Got one on my boat right now. But it's for rough water, handling, and stern lift......
 

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I believe the impression that 4 blades are for holeshot came about because most people drop an inch or two of pitch when going to a 4 blade. Sure, it should pull harder on the low end...... it's like having lower gears in the rear end of a car. All things being equal, a 3 blade should spin up quicker. It's less rotating mass. Heck, a 2 blade would beat both of them..... but balance would be an issue.

Go to any ODBA race and walk the pits. Most every boat there will have a 3 blade on it. Vast majority are probably old Yamaha drags, or some close copy thereof.

Don't get me wrong. 4 blade has its place. Got one on my boat right now. But it's for rough water, handling, and stern lift......
I still have a ton to learn about props and got into it late in the game but hopefully one day you guys will be contacting me for custom shallow water wheels.
 

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Most new props purchased today are of poor finish quality from the factory. I have come to depend on prop shops to check specs, balance and tune every prop I buy. I've had the best results with a high-rake 3-blade, with a little less pitch than others would normally have, and more cup added for grip in high trim, turns, and hole-shot. Some added tip cup is good for carrying the bow, but too much tip cup will drop the RPM too low at WOT. The important thing to remember when you bring your prop to the shop for tuning, is not to tell the expert what to do to your prop. Tell him or her what they need to know - what the prop does now - and the results you're looking for, and let the expert do what he or she thinks should be done to get those results. Also, you should always end up with a prop that allows your motor to reach the top-end of its maximum recommended RPM range, to get the best all around performance and fuel economy. Just my $0.02
 

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Most new props purchased today are of poor finish quality from the factory. I have come to depend on prop shops to check specs, balance and tune every prop I buy.
Very true. Especially the PT props

Pitch between blades can be quite inconsistent. For example, a prop stamped 16 pitch might have one blade that's 16p, one 17p, and one 15p. Only way to check (that i know of) is for a prop guy to throw it on his pitch block.

I had that Ron Hill guy that sells "signature series" props on Ebay tell me one time that was a feature, not a flaw :ROFLMAO:

Not all prop guys are created equal.
 

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I still have a ton to learn about props and got into it late in the game but hopefully one day you guys will be contacting me for custom shallow water wheels.
I would just work at jacks for free for a few months. Just do whatever he says. That first one he did (before the one you grabbed) had been heavily cupped by admiral TWICE. He asked if they had ever cupped a prop before. Came back like a spoon. I just don’t know anyone in FL that knows how to do what he does.
 

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I would just work at jacks for free for a few months. Just do whatever he says. That first one he did (before the one you grabbed) had been heavily cupped by admiral TWICE. He asked if they had ever cupped a prop before. Came back like a spoon. I just don’t know anyone in FL that knows how to do what he does.
That’s why people that are real mad at skinny water go to him or once they do they never look back. There are some really great prop shops but Jack is the shallow water prop guy. Powertech knows what’s up, that’s why they sell some of his prop designs.
If it all works out it’s going to be a great addition to the shop but he’s set in his ways and super stubborn. He did offer to teach me if I end up buying his equipment but the knowledge has to be earned by hands on experience.
 

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That’s why people that are real mad at skinny water go to him or once they do they never look back. There are some really great prop shops but Jack is the shallow water prop guy. Powertech knows what’s up, that’s why they sell some of his prop designs.
If it all works out it’s going to be a great addition to the shop but he’s set in his ways and super stubborn. He did offer to teach me if I end up buying his equipment but the knowledge has to be earned by hands on experience.
Yep, I have to believe there is room for some innovation. Either something like Chuck's six blade prop, or a small five bladed prop with stubby little blades along the lines of Mercury's High Five. Think smaller diameter. Easier to balance , less sticking below the surface of the water, less prop close to the surface of the water etc.
 

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I would just work at jacks for free for a few months. Just do whatever he says. That first one he did (before the one you grabbed) had been heavily cupped by admiral TWICE. He asked if they had ever cupped a prop before. Came back like a spoon. I just don’t know anyone in FL that knows how to do what he does.
Where would you take a prop in Florida (preferably South Florida) to have them work on it? What would you expect this to cost?
 
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