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  1. #1
    Ginger or Mary Ann? Charter Member US1 Fountain's Avatar
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    fuel pump pressure

    Do the mechanical stock pumps always pump same pressure, or does it increase with rpm?

    How much pressure can a Q-jet take before it unseats?

    Thanks


    added:

    Is it possible for a stock Merc high volume pump to put out 20psi at 2000rpm? Curious if a buddy was sold the wrong pump.
    Last edited by US1 Fountain; 07-04-2011 at 06:40 PM.
    Some people are like Slinkies - Not really good for anything, but they
    bring a smile to your face when pushed down the stairs.

  2. #2
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    Banana Pump Pressure

    Stock pump about 5 to 6.5 lbs depending on the RPM . Anything over that your asking for problems. Damaged needle and seat bent float arms from fuel comming past the seat. If your going to run a high volume pump put in a fuel regulator and set it about 5 to 6 lbs.

  3. #3
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    The pump volume increases with rpm but the presure should not exceed 7 psi on a stock mechanical fuel pump. Sounds like the pump is wrong or defective.

  4. #4
    Ginger or Mary Ann? Charter Member US1 Fountain's Avatar
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    Ok, thanks guys.

    This is a buddies boat been working on last couple weekends. stock '88 454. Dumps fuel past N/S. tried new kit, float and carb body, no change, thus eliminated carb as the culprit. He just put a press gauge on it today.
    Some people are like Slinkies - Not really good for anything, but they
    bring a smile to your face when pushed down the stairs.

  5. #5
    VIP Member VIP Member MILD THUNDER's Avatar
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    Quote Originally Posted by US1 Fountain View Post
    Ok, thanks guys.

    This is a buddies boat been working on last couple weekends. stock '88 454. Dumps fuel past N/S. tried new kit, float and carb body, no change, thus eliminated carb as the culprit. He just put a press gauge on it today.
    I get 8psi at idle. 1050 Dominator, holley 120GPH six valve marine pump. High flow needle and seats, no problems.

    However, you are working with a different animal. Sounds like he may be needing a pump.

  6. #6
    Ginger or Mary Ann? Charter Member US1 Fountain's Avatar
    My Boats:
    1999 32 Fountain Fever, 1995 Baja 29' Cruiser
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    Quote Originally Posted by MILD THUNDER View Post
    I get 8psi at idle. 1050 Dominator, holley 120GPH six valve marine pump. High flow needle and seats, no problems.

    However, you are working with a different animal. Sounds like he may be needing a pump.
    I agree now that we know what the pressure actually is. I didn't think the mechanical pump was capable of that high of a pressure, so it never entered my mind as the problem.
    A new pump is on it's way now.
    Some people are like Slinkies - Not really good for anything, but they
    bring a smile to your face when pushed down the stairs.

  7. #7
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    US1 The slinkie joke is some Funny s##t thanks!

  8. #8
    Ginger or Mary Ann? Charter Member US1 Fountain's Avatar
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    ...
    Some people are like Slinkies - Not really good for anything, but they
    bring a smile to your face when pushed down the stairs.

  9. #9
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    what kind of volume and or pressure will a factory mechanical pump from a 502mag off the water pump give???

    will it support a 502 carb motor with a 800cfm holley without the electric pump that is high pressure for the efi

  10. #10
    Offshoreonly Advertiser Offshoreonly Advertiser Mbam's Avatar
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    Some of the OEM Merc pumps are doing just that - too much pressure. We have warrantied a bunch.


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