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tunnel blow over!!!! help please!

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tunnel blow over!!!! help please!

Old 09-22-2007, 08:46 PM
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crazy maxx
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Default tunnel blow over!!!! help please!

ok i have a prather tunnel with a lap cat botoom and a different style top. the boat isnt mine its my dads.... i am begging for him to let me have it. there one problem with it. it blows over to much!!! we have a 7.5cc k&b outboard on it and it trimmed down to the max and jacked down most of the way. we cant get a full speed run with it be cause of either wind or a little wake. we got a couple with where good but at the end it stared to bounce around a lil.
any tips would be very help full!!! i will get some photos of it mabey later tonite.

i was thinking of putting the jackplate all the way down and trimming the motor up a smidge.
also mabey we are running to big of a prop??

thanks
Brett
Old 09-22-2007, 09:14 PM
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Default RE: tunnel blow over!!!! help please!

Tunnel's usually dont take to chop too well, but you can get some stick on weights (like used when getting your wheels for car balanced) and put them on the insides of the sponsons to keep the nose down. It will look ugly, but an effective way to get some more weight up front keeping the sponsons down.
Old 09-22-2007, 09:19 PM
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Default RE: tunnel blow over!!!! help please!

What your CG set too?
Old 09-22-2007, 09:27 PM
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Default RE: tunnel blow over!!!! help please!

cg???
it mosly happends because of to much lift
mabey we could try a smaller prop
Old 09-22-2007, 09:51 PM
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Default RE: tunnel blow over!!!! help please!


ORIGINAL: crazy maxx

cg???
it mosly happends because of to much lift
mabey we could try a smaller prop
CG would be the center of gravity. Where the boat balances at (distance from transom)
Old 09-22-2007, 09:58 PM
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Default RE: tunnel blow over!!!! help please!

well at the speed we run almost all of it about half of the boat is in the water
Old 09-22-2007, 11:01 PM
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Default RE: tunnel blow over!!!! help please!

you need to place the boat on a rod or broom handle or something and see where it balances (teeter-totter). mark that spot on the bottom of sponsons then measure from the transom to that spot, you'll then know exactly where the CG is.

have you tried adjusting the motor to the prop is pointing down slightly... this will keep the nose down. What prop are you using?
Old 09-23-2007, 12:06 AM
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crazy maxx
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Default RE: tunnel blow over!!!! help please!

the motor is trimmed all the way down
the prop i dont no but it looks like it has alot of pitch and it looks big ill find out tomarro
Old 09-23-2007, 07:57 AM
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Default RE: tunnel blow over!!!! help please!

pics








Old 09-23-2007, 10:18 AM
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Default RE: tunnel blow over!!!! help please!

What he is asking above is to see if the boat is too tail-heavy which may be the reason why the boat is flipping too easily. You can use your fingers on each side of the boat to give you a rough idea of where it is. Measure that spot then do some quick math. As an example only, if the hull is 30" long and the boat balanaces out at 10" from the transom, then your center of gravity is at 33-1/3%. Normally for a tuneel boat you want it at around 27-28%. On you boat in particular, the center of gravity should be where the turn fin os. BTW, I'd remove that unless the boat really needs it.
Don't forget the check the CG with the fuel tank empty.
Old 09-23-2007, 03:18 PM
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Default RE: tunnel blow over!!!! help please!

i will get the cg asap i need to find a broom or pole
Old 09-23-2007, 05:40 PM
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Default RE: tunnel blow over!!!! help please!

the cg is at the center of the turn fin
the turn fin is needed
Old 09-27-2007, 07:46 PM
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Default RE: tunnel blow over!!!! help please!

The Prather boat's main flaw is that is blows over too easily. Not much you can do to fix it. It packs too much air under it and will blow over every time you get up to speed. Time to get a newer designed hull that will handle the power. They are good play boats, but they will run you ragged trying to get them to handle properly.

~James

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