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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

  • #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

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      • #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.

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                    • #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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