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Thread: Mercruiser fuel pump/regulator help

  1. #1

    Default Mercruiser fuel pump/regulator help

    Looking for any mechanical help from the experts. So I have a 2003 Mercruiser v8 5.0l MPI. The motor is having fuel pressure issues. It runs great at top end. 3600-4000 rpm. After the testing I've done we narrowed it down to being either a fuel pump. Or fuel return regulator. The boat starts great but then begins to lose fuel pressure. (Bleeding back the return regulator???) The voltage holds at 14 so I know we're good there. Is there any way to know which one it is that's bad? I don't want to buy a pump and have it be the regulator. Or visa versa. Just curious if anyone knows any tricks to testing the two. Also it seems to start and hold fine cold but after the motor warms up is when pressure begins to go down which is why I think it could be the fuel return regulator. Also the fuel pressure gauge doesn't hold steady like on a car. It bounces back and forth. Any input or help would be appreciated. You can pm or call or text me. Thanks.

    -Adam 841-6569

  2. #2


    Also the motor seems to start and run fine when cold. But once it heats up it starts to lose fuel pressure unless I accelerate and start going. Then once up to 3000 Rpm and up it goes good. Does this sound more like a bad fuel pump or a bad fuel return line regulator? Thanks

  3. #3
    Premium Member kasilofchrisn's Avatar
    Join Date
    Jan 2009
    Central Kenai Peninsula


    I would call Marine services in Homer.
    Bill or Lee will be able to answer your question and get you the parts at the best price in AK.

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    "The closer I get to nature the farther I am from idiots"

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