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What Is Porposing????

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Old 05-31-2011, 09:26 AM
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Default What Is Porposing????

Is porposing when the front of the boat bobs up and down when your running at high speed? If so what causes it? What can you do to fix the issue?
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Old 05-31-2011, 09:50 AM
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Yes when your bow raises out of water, comes back down & repeats. The two ways i know how to fix is drive trim corrections or tab control. I also think some boats are notorious for it so may not be easily corrected. But ill let others that are much smarter than me chime in with more advice.
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Old 05-31-2011, 10:10 AM
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check the tabs and trim, the good props will help too
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Old 05-31-2011, 10:25 AM
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Originally Posted by ludo73 View Post
check the tabs and trim, the good props will help too
As far as a prop I have a Bravo 1 24p, but am starting to work with Bblades on possibly a new labbed prop. Now for the tabs I was told not to put them on my boat because it is more dangerous then helpful on my size boat. Now for the trim would you trim up or down more? Thanks for the help guys.
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Old 05-31-2011, 10:39 AM
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Well you have a cat correct? Porpoising is common with cats around 80. You usually will just have to push through the porp as it goes away with speed. It's basically the boat alternating between lift and settling.
A prop can help by creating more lift up front. Tabs can help but all they do is create drag. They are more for settling the hull in unbalanced loads or rough seas.
Porpoising is inherent in a lot of cat set ups. It can be frustrating but once you know it's coming you can deal with it.
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Old 05-31-2011, 11:44 AM
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This might be wrong, but I was told porpoising happens when the strakes are causing your boat to rise and the drive is trimmed down forcing the bow down causing your bow to go up and down all.
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Old 05-31-2011, 11:52 AM
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Originally Posted by Poker~N~Run View Post
Well you have a cat correct? Porpoising is common with cats around 80. You usually will just have to push through the porp as it goes away with speed. It's basically the boat alternating between lift and settling.
A prop can help by creating more lift up front. Tabs can help but all they do is create drag. They are more for settling the hull in unbalanced loads or rough seas.
Porpoising is inherent in a lot of cat set ups. It can be frustrating but once you know it's coming you can deal with it.
Yes I do, and I love it and it handles great, but this weekend I was out on the lake getting some numbers for my prop work and the boat was porpoising. I have never had this issue before and I was wondering if it was because the lake was like glass. It would do it when I was at my top speed around 70. So basically the only way to fix it is to add more power? Well I want more power but it will take some time to achieve. I never really run my boat that hard I'm usually around 55 -65.
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Old 05-31-2011, 12:00 PM
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A dozen things could be causing it. If you have a problem with it on your boat, we need to know:
What hull?
What props? (this is often the culprit)
How long are the tabs?
If cat, do you have a tunnel tab?
What is the X-dimension?
Do you have a notched transom? (this is often the culprit)
Has the bottom been modified? (hook or rocker added/removed, or anything else done)
Has the center of gravity been changed on the boat from original? (ballast)
Do you have extension boxes?
Have the engines been moved? (forward or back)
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Old 05-31-2011, 12:14 PM
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I thought it's what happens when your GF is on top of you on a waterbed.
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Old 05-31-2011, 01:45 PM
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[QUOTE=Sydwayz;3416302]A dozen things could be causing it. If you have a problem with it on your boat, we need to know:
What hull? 2008 Lightning Custom Boats, 27 Strike (like a Elim. Dayton)
What props? (this is often the culprit) Right now I have a bravo 1 24p (starting to work with Bblades now for a labbed prop)
How long are the tabs? No tabs, I was told they are dangerous on my size boat
If cat, do you have a tunnel tab? No, single engine
What is the X-dimension? I have no idea
Do you have a notched transom? (this is often the culprit) I have no idea
Has the bottom been modified? (hook or rocker added/removed, or anything else done) Not that I know of
Has the center of gravity been changed on the boat from original?
(ballast) No
Do you have extension boxes? No I do not
Have the engines been moved? (forward or back) No
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