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Mercruiser 5.0 MPI 2007 intermittent engine cut off issue

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  • Mercruiser 5.0 MPI 2007 intermittent engine cut off issue

    Hi everyone.

    I have a very difficult issue to resolve. Last year I purchased a 2007 Crownline 21ss with a 5.0 MPI Mercruiser Alpha drive with 420 hours.

    Full tuneup was never done on it, so I decided to do the maintenance myself and ended up replacing sparks, wires, full distributor assembly, IAC (Idle Air Control)unit, completely emptied gas tank, replaced all oils and filters. When it was all said and done my engine now has an intermittent issue where at various RPM levels the engine briefly cuts off, safety beep is heard and the RPM momentarily drops by 1000 RPM. It can do it a few times in a row and stops for 10 minutes and does it again out of the blue. At low RPM it will cause engine to stall. But it can run smoothly for 20 minutes no issues then start doing it again. Oil and gas pressures are fine and were tested in the shop.

    I have brought to 2 different mechanics and no one can find the issue because the cannot reproduce it. And it does not do it in the shop.

    I have no idea what to do anymore. I have spent $2000 with the maintenance and parts replacements and I still have the issue? What is the next step?

    I might have introduced the issue with the parts replacements, but I have had a mechanic review what was done on it and was told it looked ok.

    Help!!!

    Engine Serial Number 0W689...
    Drive Serial Number 0W89...
    Transom Serial Number 1A105...

    Thanks, Sly
    0W689770


    5.0L MPI, 2007 Mercruiser in a Crownline 21ss

  • #2
    Hi
    i know exactly what this is. It’s the shift interruption switch getting nudged monetarily by the throttle assembly at wot. I’ve commented on this a few times now after it happened to mine too. Not many beloved me. There are other incidents of this happening elsewhere too. Google 5.0 mpi wot misfire and you’ll see it elsewhere.
    Very hard to reproduce when trying to diagnose but I’d bet my bottom dollar on it.

    Comment


    • #3
      Get the boat in open water and disconnect one end of the shift interruptor and see if it does it again.
      94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
      95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
      07 Seadoo GTX
      Merc Adults Only VP Adults Only
      G-Dad always said "First Liar doesn't stand a chance"

      Comment


      • #4
        The fact that the warning horn sounds when this happens points to the ECM losing power or at least suffering a severe voltage drop.

        Many ,many things can cause this. Key switch, safety tether, 10 pin and more.

        If you post a serial number I can look to see if there any common causes for your engine.
        Good Luck Muc

        Comment


        • #5
          Serial number. 0W689770
          0W689770


          5.0L MPI, 2007 Mercruiser in a Crownline 21ss

          Comment


          • #6
            Is it ok to run engine with Interruptor Switch disconnected?
            0W689770


            5.0L MPI, 2007 Mercruiser in a Crownline 21ss

            Comment


            • #7
              Please note that my issue is not only when running WOT
              0W689770


              5.0L MPI, 2007 Mercruiser in a Crownline 21ss

              Comment


              • #8
                Originally posted by FabienLamour View Post
                Is it ok to run engine with Interruptor Switch disconnected?
                Yes, but be careful. You won't be able to shift back to neutral with it disconnected.

                Check the 50amp circuit breaker on the engine. If it is the "yellow flag" style. That could be your problem. It should be the red push button.
                Good Luck Muc

                Comment


                • #9
                  This sounds EXACTLY like something I just experienced. Mine seems to have been the circuit breaker. It was the red push button type but I had a spare and swapped it. I say "seem to be" because I only have 2 hours since it stopped but before it would go 10 minutes without acting up.

                  Comment


                  • #10
                    How can I test the circuit breaker before I yet spend money on it? Can it be bypassed?
                    0W689770


                    5.0L MPI, 2007 Mercruiser in a Crownline 21ss

                    Comment


                    • #11
                      It can happen at any throttle position but usually after half throttle. Disconnect it and see as suggested. Mine was proven by doing just this on the advice of this forum. Pretty sure it was Alldodge who suggested it. It can either be a faulty switch if not...but usually a tiny adjustment in the positioning of the assembly does the trick.
                      May be that it’s not the issue but worth a try and sounds very similar to what others and I have seen. When it happened to mine it was usually at full throttle and a really obvious cut in power. Literally cutting 4 cylinders and their ignition. Sometimes for a second and sometimes for a fraction of a second but almost every few seconds.

                      Comment


                      • #12
                        I have ordered a new shift interrupter switch without doing the testing it on open water yet. Will keep you posted.
                        0W689770


                        5.0L MPI, 2007 Mercruiser in a Crownline 21ss

                        Comment


                        • #13
                          Originally posted by FabienLamour View Post
                          I have ordered a new shift interrupter switch without doing the testing it on open water yet. Will keep you posted.
                          That’s good but like I say. It’s sometimes not the actual switch. It’s the throttle assembly coming into contact with it momentarily that does it.

                          Comment


                          • #14
                            Originally posted by FabienLamour View Post
                            I have ordered a new shift interrupter switch without doing the testing it on open water yet. Will keep you posted.
                            If the switch is not adjusted correctly then replacing it will do the same thing.

                            Disconnect the switch is not a big issue for testing. Disconnect, run and see if it does it. Slow down, turn motor off, then shift into neutral.

                            How can I test the circuit breaker before I yet spend money on it? Can it be bypassed?
                            Use a voltmeter and measure each side of the breaker. Wile measuring, giggle the wires to see if it breaks connection. Yes you can bypass with a jumper to go across the 50 amp contacts
                            94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                            95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                            07 Seadoo GTX
                            Merc Adults Only VP Adults Only
                            G-Dad always said "First Liar doesn't stand a chance"

                            Comment


                            • #15
                              Sign up today
                              Originally posted by QBhoy View Post
                              Hi
                              i know exactly what this is. It’s the shift interruption switch getting nudged monetarily by the throttle assembly at wot. I’ve commented on this a few times now after it happened to mine too. Not many beloved me. There are other incidents of this happening elsewhere too. Google 5.0 mpi wot misfire and you’ll see it elsewhere.
                              Very hard to reproduce when trying to diagnose but I’d bet my bottom dollar on it.
                              I disconnected the Shift Interrupter Switch and got the exact same issue. I took a video of the issue while driving, but cannot upload it because it is too large I assume.
                              0W689770


                              5.0L MPI, 2007 Mercruiser in a Crownline 21ss

                              Comment

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