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OMC Cobra 2.3l running issues

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    #31
    No the voltage fluctuates like this when RPM is constant, or close to constant. I’m suspecting the uneven idle to be caused by the voltage fluctuation and I’m suspecting I could lower the idle if the voltage was constant. So I’m leaning towards a new alternator. My theory is the wire harness was corroded but still functioning until I opened the plug and it got the corroded wires to break. In a way I’m happy to get it out of the equation as well . I actually ordered a new alternator few days ago. Should be arriving soon. Im thinking of Metrodrivers comments on his alternator issues and I know mine giving 7.5V output on the extra outlet used for electrical choke where it should be 12v so something is wrong with it. Just wanted to get feedback from the more experienced boaters regarding if fluctuations like this are normal or not . I’m now happy with all connections. The repair to the wire harness and a new ignition switch increased voltage in front of the resistor wire when engine is switched on and not running by 0.2V so there’s a small improvement there.

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      #32
      After you achieve a smooth idle in the 6 to 7 hundred range you need to actuate the esa switch and confirm that the idle drops by stumbling to around 450 rpm but the engine does not die.
      " WET EVER "
      1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
      mmsi 338108404
      mmsi 338124956
      "I started with nothing and still have most of it left"

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        #33
        It’s been a long time since I had to look at a electric choke but I believe your voltage is correct as the choke doesn’t use 12Vs but about half that.
        1997 Maxum 2400 SCR 5.7LX Bravo II

        Mike

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          #34
          I'm not taking it out on the water until I'm happy with how it runs on mufflers. New alternator is here. I will try it out and see if it makes a change. Hopefully it runs smoother with it and I will be able to adjust the RPM to specifications on idle. If it doesn't make the improvement I'm hoping for I will try disconnecting the ESA module from the coil again, just as a plan b to try out.

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            #35
            Originally posted by runarb View Post
            I'm not taking it out on the water until I'm happy with how it runs on mufflers. New alternator is here. I will try it out and see if it makes a change. Hopefully it runs smoother with it and I will be able to adjust the RPM to specifications on idle. If it doesn't make the improvement I'm hoping for I will try disconnecting the ESA module from the coil again, just as a plan b to try out.
            any update on if the alternator fixed your issue? I got a 88 2.3 omc as well and having this exact issue as well it runs perfect for 10-15 minutes on water than just dies and will eventually start back up after about 30-40 minutes f cool down but will only run for about 30-45 seconds

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              #36
              From a different post a guy had same issue until he found an inline fuel filter that was partially clogged.
              1989 2159 Trophy Hardtop
              5.8L OMC Cobra
              2 1/2 year restoration project after "all you need to do is put the rebuilt engine back in".
              Mountlake Terrace, WA

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                #37
                Following this post like the Bible. My 87 capri cobra 3l has VERYsimilar issues. Any luck runar?

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                  #38
                  Originally posted by runarb View Post
                  Thanks Mike, yes timing is correct, both on timing belt and also ignition timing. I have not done compression test, but when it's runs it runs really great, so I can't see how compression would change suddenly.
                  its not common, but the compression ratio can change from when the engine is cold to when it warms us.... from working with engines for many years, the 2 scenarios ive seen a few times are..
                  1, when the valves are a little too tight, the engine may have good compression while the engine is cold, but as it warms up and the metal parts of the engine expands, it can cause the valves to leak compression because they cant close all the way....
                  2, excessive carbon build up on the valve stems.... the carbon can get built up enough and glazed onto the valve stems in a way that when the engine warms up and the valve guides tighten up slightly, it can pinch the valve stem just enough to hold it open slightly,.... this is more common on engines that dont get run for very long, but it can happen on any engine that doesnt get warm enough to prevent excessive carbon from forming.....

                  but in either case here, there is usually a noticeable loss of power with no other issues... at first!..... if this is happening in a marine engine, it will usually be extremely damaging to the engine if not caught in time....

                  check the compression while its cold, then do the same after it warms up to the point to where the problem shows itself... also, you mention that have replaced a lot of the fuel system components, but also double check the system to make sure the fuel pressure is good, and that the system maintains adequate flow thru the lines......


                  NU LIBERTE'
                  Salem, OR

                  1989 Bayliner 2556 Convertible
                  5.7 OMC Cobra - 15.5x11 prop
                  N2K equipped throughout..
                  2014 Ram 3500 crew cab, 6.7 Cummins
                  2007 M-3705 SLC weekend warrior, 5th wheel
                  '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
                  Heavy Equipment Repair and Specialty Welding (RETIRED)

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                    #39
                    Originally posted by Centerline2 View Post
                    its not common, but the compression ratio can change from when the engine is cold to when it warms us.... from working with engines for many years
                    You may want to edit this, I know what you meant but some may get confused.

                    Compression RATIO is a non variable. (aside from massive carbon build up)
                    Compression PRESSURE on the other hand..
                    " WET EVER "
                    1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
                    mmsi 338108404
                    mmsi 338124956
                    "I started with nothing and still have most of it left"

                    Comment


                    • Centerline2
                      Centerline2 commented
                      Editing a comment
                      you are correct... my mistake...

                    #40
                    Just from experience you want that idle to be not more than 650 in neutral in the water, or 600 in gear, and when you trigger the ESA it should drop it to 450 rpm without the engine stalling. Any higher and it will CLUNK into gear and shifing out of gear will be stiff....When set right it drops into gear with a THUNK and comes out of gear with 2 fingers. Make sure the carb is really internally clean, idle mixture is set right, etc.
                    88 Four Winns 200 Horizon 4.3 OMC
                    98 Jeep Grand Cherokee 4.0/Selectrac
                    07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

                    Long Island Sound Region

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