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1990 Evinrude 25 HP E25RESB Low idle problems

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  • 1990 Evinrude 25 HP E25RESB Low idle problems

    I posted some about this yesterday. Just to make it clear I know very little about engines and carburetors so I may need directions to be broken down barney style. The problem I am having is that the motor will start up and run just fine at high rmp if I start it with the throttle up till the butterfly is open. It begins to run rough and will die when I get close to bring the throttle the whole way down. I have cleaned the carb and it seemed that all orifices were clear. The s/s needle valve was set at 3.4 turns from seat. I set it to 1.5 turns and it still wont run at idle. The plugs were black and dirty when I changed them out.

    I am including a picture of where the butterfly begins to open. What are the two notches for on the plastic part(don't know name)? Should it start to open at those notches?

    I thought this could be fuel pump bit it runs excellent under high rpm's. Maybe a weak fuel pump?

    Click image for larger version

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  • #2
    Re: 1990 Evinrude 25 HP E25RESB Low idle problems

    Compression is ??

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    • #3
      Re: 1990 Evinrude 25 HP E25RESB Low idle problems

      I don't have a compression tester. I'll have to get one.

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      • #4
        Re: 1990 Evinrude 25 HP E25RESB Low idle problems

        Yes it should start opening at the mark.
        Did you spray carb cleaner down all orifices to check they were patent?
        Have you checked timing or removed the flywheel to check the woodruff key aint sheared?

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        • #5
          Re: 1990 Evinrude 25 HP E25RESB Low idle problems

          I sprayed carb cleaner into all chambers and found no obstructions...it was very clean. I checked compression and have around 110 psi in both cylinders. Have not checked timing or removed flywheel.

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          • #6
            Re: 1990 Evinrude 25 HP E25RESB Low idle problems

            Do a drop test on each cylinder if you can get it running long enough.
            Drop test is pulling out the sparkplug boot while its running and seeing if that changes the engines running. Do that on both cylinders. If it will run with one plug unplugged but not the other one then you know there is a difference in conditions between both cylinders.

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            • #7
              Re: 1990 Evinrude 25 HP E25RESB Low idle problems

              Ok, tried that. it will run on either single plug. The motor runs fine, it will stall when the butterfly closes all the way....it has to have the butterfly cracked a little bit to remain running....other than that it will continue running forever with the butterfly slightly cracked open...

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              • #8
                Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                25 evinrude - YouTube

                Here is a video...after this video I realized I wasn't getting spark to my lower plug, I cleaned some wires and now have spark.

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                • #9
                  Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                  I'm wondering if the butterfly is supposed to have a little crack in it or is it supposed to be closed while in low idle.....I would think the butterfly would only be completely shut while choking....

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                  • #10
                    Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                    Completely closed while in low idle, it has a hole in it for idle airflow

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                    • #11
                      Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                      ok, any other suggestions other than pulling off the flywheel? I really don't want to get into that.

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                      • #12
                        Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                        Get your butterfly adjusted to close properly.
                        Check compression, even if you just feel for any major uneveness with your thumb.
                        Check any small hoses are not blocked

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                        • #13
                          Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                          Compression is at around 110 for each cylinder.

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                          • #14
                            Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                            Your butterfly needs to be closed at idle so do that next and check the small hoses for leaks, blockages

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                            • #15
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                              Re: 1990 Evinrude 25 HP E25RESB Low idle problems

                              The buttlerfly does close at idle, it just wont run like that.

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