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  1. #1

    Default mercury 150 outboard fuel pressure

    I have an 89 mercury 150 outboard. last fall I replaced fuel pump because fuel was being starved at full throttle after a long run. That problem is repaired but now and was an existing problem then is I am losing fuel pressure. When cold bulb will pressurize but once warmed up, bulb will not pressurize and have to choke and throttle all the way up to start and immediately throotle down after it starts but still idling up until motor sounds good and then runs good and stays running until motor is shut down again. what can be problem and how to check and repair

  2. #2
    Supreme Mariner
    Join Date
    Mar 2004
    On Barnegat Bay, NJ

    Default Re: mercury 150 outboard fuel pressure

    That is a confusing thread. However, if I did understand it, your primer bulb could be bad. You can test it by pumping it full with fuel. Now pinch fuel line behind bulb and then squeeze it forcing fuel into motor. Repeat and see if primer will get hard (still squeezing it). If so, replace primer bulb.

  3. #3

    Default Re: mercury 150 outboard fuel pressure

    Thank you for responding. I will try the bulb test but I am not quite sure I understand. When I pump up the bulband pinch the fuel line behind the bulb and pump the bulb again with line pinched forcing fuel into carb the bulb should depressurize and if it builds pressure again then the bulb is bad? I apologize if I sound dumb but I thought bulb should stay pressurized once its primed and started and if thats not true then I still have the issue with having to choke and throttle up all the way to start it and keep it running but runs great until motor is shut down again and then I have to go through the same procedure wether engine is warm or cold. I will try the bulb test tomorrow.

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