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  1. #1
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    1986 175 HP Blackmax - Injector Oil Backing Up in Fuel Line

    SN: 0B169682
    1986 Mercury 175 HP Blackmax

    After sitting for extended period, noticed oil is backing up in the fuel supply line. Guessing the fuel line had as much as 4 ounces in there.

    Been researching on this forum and am guessing I have a faulty check valve. Evidently there is a check valve that allows air to enter the block oil tank if the remote tank becomes plugged (to prevent the tank from pulling a vacuum) AND bleeds off pressure in the system when the outboard is shutdown. I suspect this check valve is my problem. Is the correct part number for this check valve 42425 4?

    Do you think the above check valve is probably the problem?

    Curious, isn't there a check valve in the primer bulb that would prevent the oil from backing up in the fuel supply line? Why didn't this stop the oil from backing up?

    Curious, how does 42425 4 work to relieve pressure on shut down. Does it constantly bleed a little pressure? If not, what causes it to bleed pressure only at engine shut down?

    Thanks for much for the help,
    Ron Maxwell

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    #2
    you need to replace both the 8781051 ck in block and 42424 4 one in block relieves psi at shut down, bulb wont stop it
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #3
    Joe, thanks for the response.

    After further study, I believe my understanding of the check valves was wrong. I will try again...

    8781051 fits in the block and relieves pressure at shutdown, correct?

    424244 is a check valve tee that will allow air into the block oil tank if a vacuum situation occurs, correct?

    If my new understanding of the check valves is correct, I don't understand why you are suggesting I replace 424244? Will you please help me on this?

    Thanks,
    Ron

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    #4
    Anyone? Bump for comments please.

    Thanks,
    Ron

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    #5
    simple age of mtr and prevent reoccurring problems, the 424244 have been know to stick open and allow oil to drain into fuel line and flood carbs, would replace both
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #6
    Joe, thanks for responding.

    If my understanding of 424244 is correct, it has nothing to do with the fuel line. Will you please explain how it sticking open would cause oil to drain into the fuel line. I'm trying to learn, not argue with you.

    Thanks,
    Ron

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    #7
    I misunderstood you ,thought you were talking about check valve where oil and gas mixed before carbs ,your asking about fitting that is inline at tank on mtr , the one I was referring to is mixing check valve needs to be replaced as well as block fitting
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #8
    does yo mtr have square fuel pump with filter before top carb
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #9
    Joe, thanks for the clarification. My motor is not the square fuel pump, it is the design 2 and the inline fuel filter is before the top carb.