Tachometer problem on my yamaha 175 2stroke outboard

[boscoe99]

There is no dedicated RPM "sensor" that I am aware of.

The flywheel has a number of magnets that rotate by coils to create electrical power.

The CDI/ECU is counting the magnet poles as they pass by the coils to determine the engine RPM. In some cases, the coil pulses are sent directly to the tachometer.

You give Yamaha much too much credit for actually having meaningful trouble shooting procedures in their service manual. Or, theory of operation even.

I suspect that what you are seeking does not exist.

[rodbolt17]

the CDI generates the tach send operating voltage.
if you lost the CPS,which only monitors crankshaft phase angle, you would also be posting about the loss of spark on at least 2 cylinders.
if your voltage fluctuation matchs engine speed I would suspect a faulty tach.

[Claus Andersen]

Hi rodbold17 / Anyone (With solving ideas)

As describet, the Green wire behind Tachometer changes voltages whit the gas OK. I have tryed with another Tachometer, still "0" RMP !?

Im lost..

I need new solution ideas.

Ty.

[Claus Andersen]

[99yam40]

Do you know if either tach works on other motors?
And are they set properly for your motor