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Late 90s Yamaha 90hp and Tach troubleshooting

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  • Late 90s Yamaha 90hp and Tach troubleshooting

    Hi, hoping that someone will be able to help me. I am a total novice when it comes to boat maintenance.

    I have a Merry Fisher 580 built in 1998 with a Yamaha 2 stroke 90hp outboard. There is a multi-function tachometer which is no longer working. The wiring Iooks ok ( all the wires from the outboard are aligned with the tachometer wires with colours matching) but I am struggling to troubleshoot as I do not have any manual. I presume the issue could be with the outboard or the tach or perhaps the battery connection.

    I want to try to validate model numbers of the outboard as a starting point. And also the tach. I wonder is there anyone here who could help based on photos?

    I think the outboard is a B90TLRW but I cannot be certain as the writing on the ID plate has worn away. No serial number available either. I would order a manual but ideally would like to be able to make sure I order the right one.

    Based on internet searches, I think the tach is a 6Y5-8350T-83-00. I don't want to remove the tach to look for a exact model number just yet. I would prefer to be able to do the research first, if at all possible.

    I am attaching some photos of the engine, the tach and some wiring at the back of the tach. Any help would be very much appreciated.

    Thanks in advance.

    Adrian
    Outside photo Lid off engine Tach

  • #2
    Couple of additional photos

    Comment


    • #3
      That is a pre -83 tachometer.

      If it does not work with battery + and - applied directly to the yellow and black wires respectively then it has failed internally.

      Power comes from the battery to the motor through a fuse to the ten pin harness and on to the key switch. From the key switch to the tachometer via a fused harness.

      www.gaugesaver.com

      Comment


      • #4
        Thank you, Boscoe99.

        I will do a test. There is a faint display on the tach every now and then, so I expect it is a tach issue.

        Could you advise what replacement part or parts could be used to replace this (still unknown) model of tachometer?

        Any thoughts on how I can identify the engine model.

        Thanks in advance.

        Comment


        • #5
          As to the engine model, look at the CDI. What numbers do you see on it?

          Comment


          • #6
            Originally posted by AdrianNeville View Post
            Thank you, Boscoe99.

            I will do a test. There is a faint display on the tach every now and then, so I expect it is a tach issue.

            Could you advise what replacement part or parts could be used to replace this (still unknown) model of tachometer?

            Any thoughts on how I can identify the engine model.

            Thanks in advance.
            Faint display could be from a low voltage issue to the tachometer. Apply battery power directly to the tachometer to see what happens.

            Comment


            • #7
              Could you help.indicate where on the engine the CDI is located?

              A few more photos might help.

              (Googled CDI ... just to confirm this stands for cacitor discharge ignition?)

              Thank you

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              • #8
                You might need to remove the cover to see the letters and/or numbers.
                zb90.jpg

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                • #9
                  Thank you, Boscoe99. Really very much appreciated. I will hopefully get to test the tach with the battery and check under that cover in the next few days and revert. Cheers.

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                  • #10
                    I found a yamaha rigging guide for 2001 with lead identification for a tachometer where the wire colours almost match the tach on my boat. See attached. I think I need to go back a few years ...prob 1997 or 1998. I wonder does anyone have a link to an earlier rigging guide? Thanks in advance.

                    Comment


                    • #11
                      Boscoe99, I found the Serial / Model no label. The previous owner had moved it. The engine is a 90AETO model.

                      I also tested the tach with direct connection to the battery. It looks like it is actually working but with a really faint LCD display. It is a new battery so I expect that the issue is with the tach itself.

                      I wonder if you could help me understand what options I have by way of replacement of the tachometer with compatible models.

                      Thanks again for your help.
                      ​​​​​​

                      Comment


                      • #12
                        Where are you located? A 90 AETO is not a model that was sold here in the USA.

                        What is the serial number?

                        Any of the Yamaha multi-function digital display tachometers that have two two white square nylon connectors should work with your motor. There are a number of them. The -83 is just one version that will work.

                        I would get it repaired or replaced by www.gaugesavers.com

                        Comment


                        • #13
                          I am located in Ireland. I believe the boat was originally a UK boat

                          Serial number on the label (under 90AETO) is 6H1 L 497237 V.

                          I will try gauge savers.com.

                          Do you know if there are analog gauges that are also compatible?

                          Thank you.
                          ​​​​

                          Comment


                          • #14
                            Serial 6H1 L 497237 is the equivalent of a 1998 USA model 90TLRW.

                            Analog gauges (Yamaha and aftermarket) and Yamaha digital display (multifunction) gauges will work.
                            z90.jpg

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                            • #15
                              Thank you.

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