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  1. #1
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    Intake Duct Issues

    Since 97, I have cracked 5 of these. It usually happens on the opposite side of what is shown in the picture and never this far up in the "tunnel". Normally it cracks near the back intake grate bolt and goes vertical towards the tunnel. As you can see in this pic, this is a pretty nasty crack. When I was bone stock I cracked 1 or 2. As my speeds have increased, it is happening more frequently. I seal in the intake duct with 3M-4200. My thinking is without this area being sealed it can cause drag all along the sides of the intake duct where it meets the hull, and it keeps this flimsy aluminum from flexing.

    On the other side of my thinking, maybe because I have it sealed in, water that would normally go by the sides of the duct is now making its way through my pump, increasing pressure, causing it to crack more frequently. For anybody who has ever removed a sealed in intake duct, you know what a job this is, and the part cost $250.00. Does anyone have suggestion on how this area could be reinforced.
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  2. #2

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    Ouch! I was thinking of pulling mine while I had it apart and sealing it up like that but I didnt want to go through the trouble and it wasnt in the FSM. My line of thinking was the same as yours though. I have never had it off to know how much room there is on the other side. Is there room to glue some kind of thin aluminum bar onto the back side? I dunno, this is my first thought of reinforcement...like 1"x1/8"aluminum.

  3. #3
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    There is room for reinforcement. After looking and thinking about it again. Sealing it up down the sides can't be causing it. From the factory it comes with weatherstripping that eventually fails. I will post a pic tomorrow of the seal job, damn its so pretty too!

  4. #4
    Moderator beerdart's Avatar
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    Maybe time for some relief valves.

  5. #5
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    Quote Originally Posted by beerdart View Post
    Maybe time for some relief valves.
    I don't guess it would hurt, but I cracked a few when it was a 60mph ski, just not this bad. I don't know of anybody on the forum that has ever done this on a GP, but maybe I should be the test mule. It would probably only take one 3/8 valve. I just don't want to lose any hole shot, he never cavitates out of the hole.

  6. #6
    Old Ski Insanity w/rpm500's Avatar
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    I'm looking at a 155 pump housing I have here.. it definatly could use some reinforcments on the backside ..its some pretty thin metal..maybe Laying up back side, kevlar or 'glass with epoxie to stiffen the area against cracking ..You could also use an old housing, cutting its tunnel up into fitted pieces, then use those as overlying plates.., stick them solid with fusor structural adhesive epoxie.. you'd have to test fit clearence feasability before glueing anything permanently in place..

    Is suction is doing this?.. that your pulling so much water at the front side of the duct and under the boat that its actually collaping??? Note that You are pulling more water than any gp duct was surely ment to do and with that PERFECTLY SEALED DUCT your not sucking any expandable air which normally gp's would let bleed in..maybe your pulling so much solid unexpandable water mass that its actually crushing it in..
    May be the FOUNTAIN BOYS have run into this in jet boats...I know that their intake ducts are a lot stouter..

  7. #7
    DAGO RACING CREW 97GPSLEEPER's Avatar
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    Quote Originally Posted by w/rpm500 View Post
    I'm looking at a 155 pump housing I have here.. it definatly could use some reinforcments on the backside ..its some pretty thin metal..maybe Laying up back side, kevlar or 'glass with epoxie to stiffen the area against cracking ..You could also use an old housing, cutting its tunnel up into fitted pieces, then use those as overlying plates.., stick them solid with fusor structural adhesive epoxie.. you'd have to test fit clearence feasability before glueing anything permanently in place..

    Is suction is doing this?.. that your pulling so much water at the front side of the duct and under the boat that its actually collaping??? Note that You are pulling more water than any gp duct was surely ment to do and with that PERFECTLY SEALED DUCT your not sucking any expandable air which normally gp's would let bleed in..maybe your pulling so much solid unexpandable water mass that its actually crushing it in..
    May be the FOUNTAIN BOYS have run into this in jet boats...I know that their intake ducts are a lot stouter..
    All of the above is possible. I have an old duct in my shop but I broke part of it getting it out of the hull, I will take a look and see if I can use it for reinforcement. I attached a pic for those wondering what area I have been sealing.
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