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Winter project: 5.0GXi-E --> 5.7GXi-? ECM

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  • Winter project: 5.0GXi-E --> 5.7GXi-? ECM

    I know August is only this weekend, but I'm starting to plan out my winter projects. I've been going back and forth about upgrading my (270hp) 5.0GXi-E engines with the (320hp) 5.7GXi-? for the extra hp and torque. I'm no stranger to building engines, I've done 4 different V8 Mustangs and Trans AMs each starting with bare blocks,machining, picking parts, assembling, installing, troubleshooting, etc. Obviously, marine spec has its differences but I'm not a beginner and I have most of the tools...

    I have prices from Michigan Motorz for new long blocks and am working with a local machine shop on prices to bore and stroke my existing short blocks and cross checking the hard parts, it looks like they are mostly all the same between the 5.0 and 5.7 GXi-E series engines with the exception being the wiring harness.

    What I need help with is the ECM. I know the 5.7s would run lean using the 5.0 ECMs, but which, if any 5.7 ECMs will work with my existing 5.0 wiring harness and sensors, etc from the GXi-E? I see that they have different harnesses, do I need to upgrade to newer wiring with the ECM?

    Thanks in advance!
    2004 Four Winns 288 Vista - powered by twin VP 5.0 GXi-E & DuoProp drives

  • #2
    I’ve never used them but I think obd2 all in one reflashes mefi controllers to the oem program you want.

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    • #3
      If you have a MEFI controller and not a 555, then it can be reprogrammed. There are a couple that say they can also do 555 but I'm still a skeptic
      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"

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      • #4
        Wasn't there someone who tried this recently and had no end of trouble?
        If it were a carbed engine I would do it but EFI and having to depend on finding the right ECU, or reflashing it, I would not do it. Too risky.
        1988 Four Winns 200 Horizon
        4.3 OMC Cobra

        98 Jeep Grand Cherokee 4.0 Selectrac
        07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

        "While air doesn't freeze....rust never sleeps"

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        • #5
          This guy seems to be able to do what you want.

          http://obd2allinone.com/mefitune.asp

          Cranchi Ellipse 21
          5.0Gi (PWTR) 1999.
          DP-SM outdrive

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          • #6
            Thanks all!

            Looks like I have the MEFI 4 controller, so it's "doable," I'm just not sure it's worth the expense and hassle. Lou C brought me down to earth... But then again, more power would be nice...

            Guess it stays on the list and we'll see what else needs to be done. The wife mentioned last night that we "need" new canvas.
            2004 Four Winns 288 Vista - powered by twin VP 5.0 GXi-E & DuoProp drives

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            • #7
              lol canvas can be as expensive as engines!
              then again, having a happy wife is certainly a wonderful thing...

              PS the single most useful upgrade if you ever have to change engines IMO is closed cooling. I have always hated raw water cooling because I am in salt water and what it does to engines is horrible if you are an engine guy which you seem to be. Closed cooling lets the engine run the way GM intended and adds probably 50% life to it, and even some fresh water can be quite corrosive.
              Not having to pull those damn drain plugs, deal with pulling off hoses in November, etc, makes the cost 100% worth it. If I ever repower this boat for SURE it will have a half system for the block/heads, and a remote oil filter mount...
              1988 Four Winns 200 Horizon
              4.3 OMC Cobra

              98 Jeep Grand Cherokee 4.0 Selectrac
              07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

              "While air doesn't freeze....rust never sleeps"

              Comment


              • #8
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                You weren't kidding! Replacing the full camper canvas with factory original from Great Lakes Boat Top isn't cheap!
                2004 Four Winns 288 Vista - powered by twin VP 5.0 GXi-E & DuoProp drives

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