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Mercruiser 350MPI idle dies after run?

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    No sir my 5.0 is long sold. If I ever complete the engine swap I will have a 383 mpi.
    1992 2452
    5.0 alpha1 gen2


      Yes, also the 350 MPI is absolutely too small in our 2858, the base weight is near 4000kg = 8800 pounds.
      If you have six people on there are problems to get vessel on the slide.

      I think also for us 383 would be much better...the bigger the better even the gas costs here 1,60€/litre , near 2USD / litre ~ 7,5 USD/ US gal.
      On the other hand bigger engine does not always mean bigger consumption.

      JT FIN


        Hello again Lineman1 & others.

        Today we have solved that 350 MAG MPI with ecm555 , 2003/2012 missfiring problem.

        I have recorded before whole ECM data using Rinda diagnostics devices.
        It was seen from curves that when the spark advance is between 26 and 32 degrees the problem starts, horrible sound and backfiring.
        Also vacuum and rpm varies all time.

        Now thinking that the distributor can not deliver the sparks to right cylinder, some kind of cross firing?

        We put the cylinder 1 against TDC line and noticed that the rotator was not pointing enough accurate for cyl 1, shown service manual 31 page 4B-13.
        So we adjusted one teeth forwards but it was also not on the adjustment area, is was on the other side of the allowed area than before?

        Maybe the distributor gear was assembled 180 degrees wrong (4B-11) or camshaft timing is wrong, which I dont believe.

        New Vortec motor was changed 2012, maybe this needs different kind of distributor, now it was the original Mercruiser type?

        In any case I decided to modifye the Distributor Hold Down Clamp and grind a "long hole" for bolt.

        No I got the distributor rotator adjusted to point cyl 1 and between the shown lines in Service Manual 31.

        With these MPI engines you can not turn the distributor, the clamp prevents that, fixed assemly (mine now not any more...).

        So when the ECM puts more spark advance the spark goes to closer pin, not the right one ---> missfiring.

        Lineman1, Rinda diagnostics was now very important to get this solved, especially the recorded curves.

        Get some hours to least from me. Do not hesitate to ask features You like to use.

        Thaks for all, have to go boating, +22 degrees outside (water only +18...)

        br JT FIN