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    OMC Cobra 2.3l running issues

    Hi,

    I bought my OMC cobra about 5 years ago. When I bought it I replaced main ignition parts adjusted the timings, rebuilt the carburetor and etc. About 3 years ago I started to have some running issues. Boat would run great when cold, but after about 30 minutes of running it would stall. Normally I have managed to get it up and running again. Then it has been lacking power and I have for instance had to lift the propeller up close to the water level for the engine not to stall again (this trick puts less load on the engine). I have now replaced everything in the fuel system (rebuilt carburetor, new fuel pump, new filter housing, new fuel pickup tube from tank, new anti-syphon valve and all new transparent fuel hoses so I can see there is fuel in them(no vapor lock). I was convinced the issue was fuel related, but I think I have eliminated that cause.

    The ignition parts I have previously replaced is: coil (the original coil is now re-installed), cables, plugs, points, cap, distributor, condenser. I have also tried an external resistor instead of the resistor wire, but my issue is still a mystery.

    Anything that I'm missing? The good thing is that the boat now has a lot of new parts :-)

    I appreciate the help.

    #2
    Have you verified ignition and cam timing. This is a overhead cam engine with a timing belt, Ford pinto engine. I would perform a compression test to get a understanding of its health.
    1997 Maxum 2400 SCR 5.7LX Bravo II

    Mike

    Comment


      #3
      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.

      Comment


        #4
        The only thing I haven't touched is the ESA module. A) I was wondering if the ESA could cause trouble like this? How would I disable the ESA module? Will removing the wire from the ESA module to the negative side of the coil disable it? I appreciate an advise on this. B) Also if I need to replace the ESA module would it be beneficial to change over to electronic ignition? Can I buy a complete kit of new ESA and electronic ignition that works together? C) With electronic ignition should I then remove the resistor wire? I appreciate any advise on questions A, B and C.

        Comment


          #5
          My vote based on car experience is your distributor cap / rotor. Had a car that ran great when cold, but once everything heated up and expanded it would quit.

          Have you checked your cooling system? Impeller? Anything there that restricts waterflow and causes overheat and binding up?
          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

          Comment


            #6
            Thanks for the advise. I will try to install the old rotor and cap and see if it makes a difference. I have replaced the impeller few times during the last 3 years. Last time this spring before the season. I have also replaced the thermostat and the thermometer doesn't indicate overheating. Also when running on mufflers water returns warm, so I think the water flows as it should. I appreciate if someone could advise me on how to bypass the ESA or Shift Assist Module. It looks on the electrical diagram that disconnecting it from the negative side of the coil would do the trick. I appreciate if someone can confirm so I can test it next time the issue comes up.

            Comment


              #7
              Yes, you can eliminate the esa by removing its connection to the negative side of coil....BUT...and it's a large one...

              You will need to shut the engine off to shift OUT of gear.

              " 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


                #8
                Rereading previous post, I would be suspicious of the ignition coil. These heat up and can have a voltage breakdown when their bad.
                Last edited by builderdude; 06-19-2022, 10:43 PM.
                1997 Maxum 2400 SCR 5.7LX Bravo II

                Mike

                Comment


                  #9
                  Thanks everyone. I have at least 3 things to test. The cap and rotor, the ESA by trying to disconnect it when this happen next. And the ignition coil. If it's the ignition coil then I have two bad coils as this has happened with both the new and the old installed, but I guess it can also be the case. I also have the stern drive repair manual and I might just as well go through all the electric trouble shooting tests suggested there to see if I find anything out of the ordinary. Thanks again, Runar.

                  Comment


                    #10
                    Coils rarely go bad. The way the ESA system works is that it lowers the idle speed when you attempt to shift from Fwd or Rev to Neutral. This allows the clutch dog to release the gear you’re in so the gear case will go into neutral. If the ESA sticks on when you’re in gear you can have stalling or a failure to accelerate. On mine what I found was the small buttons on the 2 ESA switches wore to the point where the ESA was sticking on. I replaced both switches and the old ESA module. If you need to replace these parts & can’t find OE parts CDI electronics sells them. It also helps to have an OMC shop manual to properly adjust the switches. The engine should be in good enough tune so that if you trigger the interrupt switch in neutral the engine will drop from 600 rpm to 450 rpm but not stall.
                    You can switch to an electronic distributor on most engines but i have never seen one for the 2.3 liter Ford that was marine rated. I stayed with points on my 4.3 V6. Points can be reliable if maintained.
                    The Cobra system works well if you know the quirks & keep the shift cable & ESA in adjustment,
                    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

                    Comment


                      #11
                      Thank you all. My mystery continues. I considered replacing points and other ignition parts, but then decided to go for electronic ignition and an ESA module that goes with it. The engine started on first attempt after the replacement. Ignition timing was a little off as expected but I adjusted it to the specification after the engine got warm. It ran a little longer and then it stopped as usual and wouldn't start again. I decided to try some of the advises I have got and replaced the coil first and then the cap and rotor and neither of the changes got the engine up and running again. I also tried to disconnect the new ESA from the coil just in case the old sensors were the cause. I decided to call it the day and try again later. At least this failure is now happening pretty consistent and seems to be getting worse and worse, so hopefully it will help me finding the cause. As I mentioned earlier I'm quite confident it's not fuel related as everything is new on the fuel side. Must be electrical. Next time I will use the stern drive manual and systematically do the tests mentioned there on the electrical system. Anything else you can think of?

                      Comment


                        #12
                        Can it be alternator related? During start the coil gets power straight from the battery, but when it is running it gets power from the alternator via a resistor wire.
                        When I first tried to start my rebuilt engine I had all kind of problems with it. Thought it was ignition, or esa or wiring and kept digging until I replaced the alternator. Problem solved. It had a problem in the field wiring. No autopart store could test it, bought a new one with the intent of returning it if if did not solve my problem. It did solve my problem.

                        For your situation consider ignition switch and its connections (provides feedback to the alternator field and coil), alternator itself and all the wiring on the back of it (corroded or broken wires at their terminals create all kind of problems, wires break at the connector and make a lose contact until there is too much resistance), check your resistor wire to the coil (which you replaced) from the alternator, finally the alternator itself. If you buy a new alternator make sure it is marine rated (ignition shielded, aka no flying sparks that could ignite fuel fumes).

                        Recently my engine did not want to stay running (started just fine) and one of the guys on here led me to the man-overboard switch. It had gone bad. My switch was a pull-to-break type of of switch, when the lanyard gets pulled it breaks the feed to the alternator field, which kills the power to the ignitor coil (this switch always has current going through it). A replacement was hard to find. Most man-overboard switches are pull-to-make switches, which don't carry current until the lanyard gets pulled and a circuit is made that grounds the ignition. These are used on jetskis and newer boats.
                        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

                        Comment


                          #13
                          Thanks, I will continue the search. Starting at the ignition switch, the man-overboard switch and so forth. The stern drive manual is good for troubleshooting. I will read it through and label all voltage and resistance tests they mention and in the end I will find the cause. I did this 5 years ago and found some connections that needed a little love and I also replaced the fuse box, the alternator ,among other items.

                          What about the exhaust riser? If it was rusted through would it give trouble like this? Meaning motor always starting up but stopping when warm?

                          Comment


                            #14
                            I think if your exhaust is rusted through you'd find water in the oil.
                            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

                            Comment


                              #15
                              Ok, that's really great to know. No water in oil so I'm very happy to be able to strike it off my list.

                              Checked man over board switch and it was suspicious so I bypassed it for testing purposes. Replaced few connections where I felt it was needed. I'm going to replace the ignition switch as well, it may not be needed but it's cheap. I ran the boat for 1 hour on mufflers. I guess I should have used the time to measure voltage at different spots, alternator outputs for instance. After an hour it stopped, but started again even though the start was rough and it needed full throttle resulting in very low RPM for a minute and then it gained power again. I was running out of time, but managed to measure voltage at the automatic choke and it was only 7.6V. This is coming on a separate output from the alternator. The second output is to the coil, so this will be my next task to measure voltage at the alternator outputs. Alternator is charging the battery fine and it's 5 years old. Hopefully I'm getting closer to the source of my issues.

                              One question, for testing purposes and also if stuck on the water, could I run power from the battery directly to the resistor wire on the coil to get motor started?

                              Comment

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