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Any Downsides To Downturns ?

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Old 04-27-2008, 02:20 AM
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Default Any Downsides To Downturns ?

i'M TRYING TO FIND OUT IF ANYONE HAD THE TROUBLE AND WHAT CAN BE DONE ABOUT WATER SUCKING UP DOWNTURNS FROM VALVE SPRING FAILURE (OR ANY OTHER MAILFUCTIONS FOR THAT MATTER) .
i GOT WATER USING THEM WITH A DRY CMI E-TOP SYSTEM .
THEY REALLY QUIET BOAT AT IDLE AND REDUCED SOME COCKPIT NOISE ON PLANE , i DIDN'T GET ANY POWER LOSSES . BUT SOME MODIFICATION NEEDS TO BE MADE TO PREVENT SUCTION DURING ADVERSE
ENGINE CONDITIONS , OTHERWISE I 'M SCARED TO REPLACE
THEM ( LAW ENFORCEMENT TICKET WAY LESS THEN ENGINE BUILDER TICKET !) CAN ANYONE HELP

THANKS AND BEWARE
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Old 04-27-2008, 07:23 AM
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drill 2 small holes in them above water level, they are great for high hp engines without power loss
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Old 04-27-2008, 07:27 AM
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usually a couple of holes on the top of the elbow will release some of the backpressure in the pipes..It is a exspensive trial and error process but it should help>>>
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Old 04-27-2008, 05:29 PM
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I run down turns on two boats. One with mild power and the other wild power. Zero issues and no holes drilled.
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Old 04-27-2008, 08:56 PM
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Originally Posted by kgshooty View Post
drill 2 small holes in them above water level, they are great for high hp engines without power loss
THE HOLES WERE THERE AND STILL GOT WATER IN ENGINE
WITH BAD VALVE SPRINGS!
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Old 04-27-2008, 09:05 PM
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Originally Posted by Brad Zastrow View Post
I run down turns on two boats. One with mild power and the other wild power. Zero issues and no holes drilled.
Brad,

the small holes come drilled from the factory on my gibson pipes . the problem came from defective valve springs
in one of my motors . I belive that without the downturns
no water could come to heads with dry exhust alone .

Howard
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Old 04-27-2008, 09:07 PM
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I was wondering if holes would work on a fountain given the fact the stock exhaust exit with 1/4 of an inch submerged. Nauti how big are the holes in your exhaust and what kind of motors and exhaust are you running?
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Old 04-28-2008, 01:41 AM
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I was wondering if holes would work on a fountain given the fact the stock exhaust exit with 1/4 of an inch submerged. Nauti how big are the holes in your exhaust and what kind of motors and exhaust are you running?
I think the holes are 1/4 " , my old set up 650 hp 509's w/ b&m 250's , e tops with cmi dry tails into downturns.

Just to be clear the pipes worked great ,BUT when you motor
malfuctions look out ! the water could be coming in your engine like you have thru prop exhust .

Still waiting to hear from gibson about this
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Old 04-28-2008, 07:45 AM
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I've never used them but I like the concept. My only issue would be if you don't have a secondary water dump or water pressure guages, how do you know your circulating water properly? I always start the boat, watch for oil pressure and then head to the swim platform to watch for water out the exhaust. I can also get a good feel for when I have an impeller starting to go bad by the time it takes to get water and the volume of water by watching the exhaust.
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Old 04-28-2008, 08:32 AM
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Originally Posted by Nauti By Nature View Post
THE HOLES WERE THERE AND STILL GOT WATER IN ENGINE
WITH BAD VALVE SPRINGS!
Make sure you pressure test your headers it might not be your down turns.

I have never got issues with mine in about 120 Hours.
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