Late 90s Yamaha 90hp and Tach troubleshooting

[AdrianNeville]

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

[AdrianNeville]

Couple of additional photos

[boscoe99]

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

[AdrianNeville]

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.

[boscoe99]

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

[boscoe99]

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.

[AdrianNeville]

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

[boscoe99]

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

[AdrianNeville]

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.

[AdrianNeville]

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.

[AdrianNeville]

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.

[boscoe99]

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

[AdrianNeville]

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.

[boscoe99]

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

[AdrianNeville]

Thank you.