Little Help
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Little Help

  1. #1
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    Default Little Help

    I have a 19 cp with a 468 ,tunnel ram and two 750 carbs when i hit 5800 rpms it falls on its face and backs down to 5200 rpms. If i let of the throttle it will catch again but will only run up to around 5200 rpms. Any thoughts?
    Last edited by BACK2BIGRIVER; 08-15-2010 at 10:14 AM.

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  3. #2
    Senior Member lbhsbz's Avatar
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    What do you have for a fuel pump?

    Is it an abrupt loss of power or a gradual drop down to 5200?

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    Probably fuel pump, also how big are your fuel lines.

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    Senior Member zacho!'s Avatar
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    have you tried changing jets?

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    Senior Member jetboatperformance's Avatar
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    X's 3 fuel supply issues , check pressure and volume ..

  8. #6
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    Pump is slipping on the hit, then catches up?

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    Purple headed member Quickjet's Avatar
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    Could also be the type of fuel line. If you have a good pump, you could be sucking the fuel line closed.
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    Senior Member Filucky's Avatar
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    Quote Originally Posted by moppy View Post
    Pump is slipping on the hit, then catches up?
    Most likely blowing the pump out on the start but soon as you get a little speed going to "load" the pump your rpm drops to where it should be. What kind of hp are you making and what cut impeller? That info would help alot. Is it just out of the hole it revs higher? If your at cruising speed and hammer the throttle does it go to 5200 or 5800? If your running out of fuel due to too small of pump or lines or whatever you will most likely get "lean pops" coming from the carb side, sounds like your ignition is taking a crap on ya, and if thats the case you better get it fixed becuase that will tear up a motor in a hurry. Also if your running lean, your motor will run hot, and your headers will be smoke'n hot!
    Last edited by Filucky; 08-15-2010 at 06:52 AM.
    Nice!

  11. #9
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    Fuel floats too low?

  12. #10
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    Quote Originally Posted by lbhsbz View Post
    What do you have for a fuel pump?

    Is it an abrupt loss of power or a gradual drop down to 5200?
    Brad
    The fuel preasure is at 7lbs. i would say it is a abrupt loss of rpms.
    Last edited by BACK2BIGRIVER; 08-15-2010 at 10:07 AM.

  13. #11
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    Quote Originally Posted by Filucky View Post
    Most likely blowing the pump out on the start but soon as you get a little speed going to "load" the pump your rpm drops to where it should be. What kind of hp are you making and what cut impeller? That info would help alot. Is it just out of the hole it revs higher? If your at cruising speed and hammer the throttle does it go to 5200 or 5800? If your running out of fuel due to too small of pump or lines or whatever you will most likely get "lean pops" coming from the carb side, sounds like your ignition is taking a crap on ya, and if thats the case you better get it fixed becuase that will tear up a motor in a hurry. Also if your running lean, your motor will run hot, and your headers will be smoke'n hot!
    I am making somewhere around 600 hp. The boat runs hard out of the hole all the way up to 5800 rpm then it drops off to 5200. Also i didn't have this problem last year it would run up to 5800 rmp and stay there.
    No popping noise just a lost of rpms

  14. #12
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    Quote Originally Posted by jetboatperformance View Post
    X's 3 fuel supply issues , check pressure and volume ..
    The fuel pressure stays at 7lbs what is the best way to check the volume?
    Thanks

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