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  1. #1
    Registered mcrsr's Avatar
    My Boats:
    1987 32 pachanga
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    Sep 2005
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    psl, fla
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    need help- suffering reversion!!!

    i just put together a stock 454, mercruiser, used a 350 hp cam, 049 heads, stock intake, qjet, thunderbolt 5, etc, w/ stainless marine exhaust, with the motor running i can see it pulling water back into the engine, if i take the riser off the inside of the manifold is wet, both sides- all parts pressure test good, if i use a piece of 3" hose and extend the dry side of the riser i see no water coming out( doesn't have a chance to mix w/ water), so i know it is not an internal leak in the engine or exhaust, compression and leakdown are good, i don't have any tight rocker arms-why is it doing this??? could it have something to do w/ the egr passage??? i mean, it roughly joins the 2 banks together, should i close off this passage??
    Last edited by mcrsr; 05-27-2007 at 09:37 AM.

  2. #2
    Registered mcrsr's Avatar
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    1987 32 pachanga
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    nobody has any suggestions???

  3. #3
    Registered H2Xmark's Avatar
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    1997 Fountain 35 Lightning
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    what are the specs on your cam, and what is your idle rpm?

  4. #4
    Registered
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    Sep 2006
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    439
    You need a 14" drop from the top of the riser to the bottom of the tailpipe. That is what Mercury Racing calls for.

    Gregg Reichman

  5. #5
    Charter Member # 55 Charter Member Griff's Avatar
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    ............................... 32 Active Thunder
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    What are the exact numbers on the cam????

  6. #6
    Registered mcrsr's Avatar
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    1987 32 pachanga
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    this motor is stock, it has a mercruiser 350 hp cam

  7. #7
    Registered PatriYacht's Avatar
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    94 43SC Black Thunder
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    That cam shouldn't give you problems. Did you get a valve job? Leakiing exhaust valves make reversion worse. Too low idle speed will too. Try 800 rpm.

  8. #8
    Registered
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    4 BOATS KILLED :)
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    May 2002
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    MIAMI, FL
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    You have something going on. We sell that set for the 365 Magnum and the EFI motors. If your risers are very old, they might be the old style where the inner pipe doesn't extend beyond the outer pipe. If you would take a digital picture and forward it to '[email protected]', I'll try to help you.

  9. #9
    Registered mcrsr's Avatar
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    1987 32 pachanga
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    psl, fla
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    i'll try to post some pics tonite, the inner pipe extends beyond the outer by roughly 2"

  10. #10
    Charter Member # 55 Charter Member Griff's Avatar
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    ............................... 32 Active Thunder
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    Is the engine/boat sitting at the same angle as it would be if its in the water??? If the bow is down, the lesser angle will allow water to revert.


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