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  1. #1
    mmo jo

    Water pumps vs cross overs on hp 500 efi.

    Has anyboudy changed out a water pump on a hp500 efi. for a cross over?What happend? More mph.? More rpms?

  2. #2
    GOT MERC? Goodfella's Avatar
    Join Date
    Aug 2001
    Boynton Beach FL
    It's really not a good idea,becaues you have a water temp sender on your 500 EFI that gives info to your ECM for timing adjustments and fuel curve. The engine will problably not run at operating temp and you will confuse the computer and gain nadda.

  3. #3
    Charter Member #1093 Charter Member SteveDavid's Avatar
    My Boats:
    2003 60' SeaRay, 2014 30' Concept CC
    Join Date
    Feb 2001
    Lighthouse Point & Ocean Reef FL
    Goodfella is right on target. Unless the ECM is re-programmed your engine will run terrible and you'll lose performance.

    We removed the circ. pumps when installing the Whipples. however the ECM's are re-programmed. The operating temps drop to less than 120 degrees. This is done primarily to reduce the possibility of detonation and increase the density of the fuel charge.

    There is a slight increase in moisture on the tops of the rocker arms until the engine generates internal heat. If your engines are not supercharged, you'll probably have longer engine life and reliability running at the thermostat controlled 140-165 (depending on your application.) If you run in predominantly colder climates, both air and water, the cold temps and cold oil could wreak havoc.


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