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1985 Evinrude 8 Hp 2 stroke - coil break down?

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  • 1985 Evinrude 8 Hp 2 stroke - coil break down?

    My tender's Evinrude 2 stroke starts easily and runs a dream when in the flushing tank back at home. As soon as it is in the water and engaged into gear with a bit of throttle / engine loading on it will only run on one cylinder. If throttle is applied further the motor surges and dies as the second cylinder comes into play and drops out again. I suspect an ignition issue but have no real experience in outboards. Are the coils in these engines prone to break down or am I barking up the wrong tree? Is there any method to verify if the coils are within spec (Ohm readings etc). Other than plugs what else could be causing an ignition breakdown?

    This may be relevant or not. The issue has just started happenning. In the first instance the breather cap on the fuel tank had not been loosened and the motor started exhibiting these issues and maintained poor performance for the run back to shore before full performance was returned (a total of a 20 minute run). In the second instance the fuel hose connector was not on correctly and caused fuel starvation, the motor has not returned to normal performance. I know this points to a fueling issue but once the fuel was returned correctly the motor did not return to normal running this time, nor has this issue been apparent when running the carb dry ofter a fresh water flush at the end of the day previously. The motor is not seized, turns easily and compression is good. I know spark resistance is related to gas mixture, compression /pressure and so might be the cause of a borderline coil to fail?
    Last edited by BruKen; May 6th, 2014, 06:55 AM.

  • #2
    Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

    With no experience in outboards, I'd take it into a shop and get an opinion.

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    • #3
      Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

      Originally posted by BruKen View Post
      My tender's Evinrude 2 stroke starts easily and runs a dream when in the flushing tank back at home. As soon as it is in the water and engaged into gear with a bit of throttle / engine loading on it will only run on one cylinder. If throttle is applied further the motor surges and dies as the second cylinder comes into play and drops out again. I suspect an ignition issue but have no real experience in outboards. Are the coils in these engines prone to break down or am I barking up the wrong tree? Is there any method to verify if the coils are within spec (Ohm readings etc). Other than plugs what else could be causing an ignition breakdown?

      This may be relevant or not. The issue has just started happenning. In the first instance the breather cap on the fuel tank had not been loosened and the motor started exhibiting these issues and maintained poor performance for the run back to shore before full performance was returned (a total of a 20 minute run). In the second instance the fuel hose connector was not on correctly and caused fuel starvation, the motor has not returned to normal performance. I know this points to a fueling issue but once the fuel was returned correctly the motor did not return to normal running this time, nor has this issue been apparent when running the carb dry ofter a fresh water flush at the end of the day previously. The motor is not seized, turns easily and compression is good. I know spark resistance is related to gas mixture, compression /pressure and so might be the cause of a borderline coil to fail?
      when was the last time the motor was properly serviced? "compression is good" doesnt cut it! what are the numbers? from what you describe, it sounds like the carb could be full of gunk, and if it hasnt been properly cleaned and kitted in years , thats where to start. those, or any ob, do not like stale , water laden fuel sitting in the float bowl over the off season. the bowl will rust/flake and plug things up.
      many men fish for years without ever knowing its not about catching one.

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      • #4
        Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

        The high speed jet sets in the bottom of the bowel, it doesn't take much to plug it up.

        Comment


        • #5
          Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

          Thanks for the answers. The motor was serviced at the end of last season in November by a dealer and I've put about 20 hours on since. She has always been ultra reliable.

          And fair comment Boobie. I have no experience in outboards and particularly 2 strokes but I am familiar with engines and mechanics in general. My issue where I'm struggling is I cannot load the motor at home to verify any changes I've undertaken. Doing them at sea has an element of risk, the dealer considers these motors obsolete because it's not the latest fuel injected yadda yadda yadda "jet ski" yadda and quite frankly isn't really interested. With that attitude I'd rather undertake repairs myself where I know that the job is done properly rather than expedited through the door.

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          • #6
            Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

            These ignition coils are very reliable !!--------So do a proper spark test and see if ignition will jump an actual gap of 7/16" or more.--Laying the plugs on the block is " fools gold " as far as spark quality.-----Post the actual compression values.--------Has water pump been serviced ?------------Get the motor running and as a test remove the gas line, how and how long does it run ?-----Good trouble shooting is the path forward !

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            • #7
              Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

              If you think its tending to run on only one cylinder identify which one by pulling the plug leads one at a time.

              If/when confirmed swap over the plugs then the coils ( two separate coils on that model I believe) See if fault moves with plug or coil.
              You cannot test them adequately with an ohm meter.


              You are using the correct plugs? Champion QL77JC4 or QL86C, gapped at 0.030"
              Not using NGK(or other brand) resistor plugs ? It wont like those
              Last edited by Vic.S; May 7th, 2014, 08:16 AM.

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              • #8
                Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

                Originally posted by racerone View Post
                These ignition coils are very reliable !!--------So do a proper spark test and see if ignition will jump an actual gap of 7/16" or more.--Laying the plugs on the block is " fools gold " as far as spark quality.-----Post the actual compression values.--------Has water pump been serviced ?------------Get the motor running and as a test remove the gas line, how and how long does it run ?-----Good trouble shooting is the path forward !
                I'll try your spark plug test.
                Compression is 102 and 96 PSI
                New water pump at last service. Good tell tale
                If I remove gasline and leave on idle she will run for well over a minute and closer to two. I haven't timed it as such but I know I get bored of waiting for it and will up the throttle some to hasten it along.

                Comment


                • #9
                  Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

                  Originally posted by Vic.S View Post
                  If you think its tending to run on only one cylinder identify which one by pulling the plug leads one at a time.

                  If/when confirmed swap over the plugs then the coils ( two separate coils on that model I believe) See if fault moves with plug or coil.
                  You cannot test them adequately with an ohm meter.


                  You are using the correct plugs? Champion QL77JC4 or QL86C, gapped at 0.030"
                  Not using NGK(or other brand) resistor plugs ? It wont like those
                  Plugs are indeed champion QL77JC4 - They do appear a bit oily. I mix oil at 50:1 and not 100:1
                  Swapping the plugs makes no difference, both fire in the flush tank - not tried it in open water yet nor tried swapping coils round
                  Last edited by BruKen; May 7th, 2014, 10:45 AM.

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                  • #10
                    Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

                    Thanks for all the responses, really appreciated.

                    I will check and clean carb and jets.
                    Check all hoses are not letting air in / dry rot
                    Swap out plugs...again ... and rotate coils to see if problem persists (yes it is two coils off CDI)
                    Check all wiring for connectivity

                    When I get some of these answers I will advise or update on what the problem is/was. Thank you all again
                    Last edited by BruKen; May 7th, 2014, 10:44 AM.

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                    • #11
                      Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

                      Disregard the sticker and manual that say 100:1 and run this motor at 50:1.----There was a service bulletin that came out years and years ago to go back to 50:1 on that motor.----------Testing is the path forward.

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                      • #12
                        Re: 1985 Evinrude 8 Hp 2 stroke - coil break down?

                        You don't have to go to sea to load the engine, tie it to the dock and apply power, that will load the engine just as well as going to sea to test for a miss.

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                        • #13
                          Hi. I said I would update when I located the problem. It wasn't coil breakdown so much as a bad signal wire between the CDI and coils. I suspect that the wire has corroded beneath the insulation as a gentle manipulation of the offending wire and the motor storms ahead as it should. Is it worthwhile trying to splice in a replacement wire lead or just replace the cdi unit as a whole? I've held off cutting the wire and replacing it in case it's a no-no and there's no return.

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                          • #14
                            BTW the wire in question looks just like mini HT leads. i.e. may be shielded hence my relcuctance to cut.

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                            • #15
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                              I have an Evinrude 4 two stroke two cylinder and would like to wire in a kill switch to both cylinders please can anyone suggest the wiring diagram to use?

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