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Gas in raw water pump oil reservoir

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  • Gas in raw water pump oil reservoir

    Hi all,
    (merc 454 7.4l 1996 of809461 with bravo iii)

    last yr. I serviced the oil reservoir in the raw water pump , and found some gas mixed w/ the oil. (i have the mechanical fuel pump that sits on top of the raw water pump). There was never any gas in the clear tube to the carb. I changed the mechanical fuel pump.

    This year, i serviced the raw water pump, and again found gas mixed w/oil! The clear tube does't have any gas going to the carb.

    It appers to be an enginering design flaw. Can i do anything to prvent this problem?



    p.s. Thanks to all the fine people who have posted on this site, i have learned lots and fixed several issues over the years. (hydrolock, bellows ,gimball bearing,allignment,u joints, shutters, impeler, lower unit service, etc.)

  • #2
    Re: Gas in raw water pump oil reservoir

    It appers to be an enginering design flaw.
    Yes it was, right up there with a 470.
    Every fuel pump leaks a slight amount of fuel into the oil pan from a block mounted fuel pump. But it's a large space and never noticed. But Merc decided to put it into a 600 dollar housing so it would need replaced every couple years.
    If your pump bearings are still good, put in new gear lube and make a cover to block it off.
    Then install an electric fuel pump with the proper oil pressure switches and plumbing and never have to spend 1200 bucks again for a fuel and water pump change on a big block.

    The proper marine fuel pump should be wired in like this.

    Don S.

    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.


    • #3
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      Re: Gas in raw water pump oil reservoir

      Thanks don s.

      I"ll look into that. Any suggestions on the pump and where i can get it?

      Paul 22