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Thread: Loss of Power

  1. #1

    Default Loss of Power

    So after 7months of not fishing and completing my engine rebuild I have run into a problem. The engine is a marine power 5.7 mpi. I got 2 trips out on my rebuilt motor and have a problem I and my mechanic can not diagnose. On my last trip out I was running at about 3700rpm for about 15 minutes when engine suffered a loss of power. The rpm's dropped to 2500 and would not increase. I immediately returned to the dock. I returned with my diagnostic computer program and hook up to engine to find a trouble code for misfire cylinder 1.

    I contacted my mechanic and he said he would take a look. He cleared code and took boat out for test run and it ran great for about 10 minutes and then had loss of power and would not accelerate above 2500rpm. He returned to dock checked computer and once again there was code for misfire cylinder 1. He checked high pressure fuel pump, rail pressure, replaced cap and rotor, plug and plug wire and still on test run it does the some thing. He thought it could be a bad injector but we agreed the computer would have thrown a different code for that and not misfire.

    Does anyone have any ideas of what could be causing this issue? I did have a broken lifter spring on cylinder 2 which required spring, oil seal and rod to be replaced a few weeks ago which we addressed and everything seemed to run good following that repair.

    Thanks in advance

  2. #2
    Join Date
    Sep 2008
    Maryland - USA

    Default Re: Loss of Power

    not knowing which year you have makes it a bit tough on those that can't see what you have.

    I don't understand how you can rule out an injector without a bit more diagnosis. I would say if it starts up after sitting, and runs ok, then its not likely to be mechanical. Was the fuel pressure checked during the test run, after the DTC was cleared?

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