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2003 F90TLRB - Yellow Wire to TCI/CDI and Tach Signal ???

newboater67

Contributing Member
What is the purpose of the yellow wire that is connected to ground and the 8 pin (middle) connector on the TCI/CDI ??? I'm curious since it's the only ground wire that's connected through a bullet connector and could be disconnected by itself.

It's also my understanding that this motor uses a TCI instead of a CDI to control the ignition timing, and the tach signal is generated by the TCI.

From searching the internet, it appears the pulser coils provide the crankshaft position and RPM which are used by the trigger circuits for the ignition coils.

Does anyone know if the tach signal is derived specifically from Pulser Coil #1 or Pulser Coil #2, or if the TCI actually samples the input form both coils to generate the tach signal?
 
In most Yams the tachometer signal originates with the lighting coil. In your model it is fed to the CDI and then on to the tachometer in the green ten pin wire.

The F90TLRB uses a CDI.

After all else fails, read the owner's manual.

 
Thank you boscoe.

I thought this motor would have a CDI but someone else told me it had a TCI and an inductive ignition so I relied on their experience, but they achieve spark by different means. It's still a black box though, so all you can really do is check the ins and outs.

So the tach signal comes from the lighting coils, thru the regulator, to the CDI, and gets modified or passed on by the CDI to the tachometer.I've traced every wire in the motor, so it has to come out of the CDI on a Pink wire in the 8-pin connector on my CDI. It's also a pink wire to the tach on my boat for some reason.

My yamaha tach needle will swing full scale and return to the running rpm intermittently. I've already checked all the wires and connections from the motor to the gauge, so will have to scope the lighting coils, regulator output to the CDI, the CDI output, and the signal at the tach.
 
Thank you boscoe.

I thought this motor would have a CDI but someone else told me it had a TCI and an inductive ignition so I relied on their experience, but they achieve spark by different means. It's still a black box though, so all you can really do is check the ins and outs.

So the tach signal comes from the lighting coils, thru the regulator, to the CDI, and gets modified or passed on by the CDI to the tachometer.I've traced every wire in the motor, so it has to come out of the CDI on a Pink wire in the 8-pin connector on my CDI. It's also a pink wire to the tach on my boat for some reason.

My yamaha tach needle will swing full scale and return to the running rpm intermittently. I've already checked all the wires and connections from the motor to the gauge, so will have to scope the lighting coils, regulator output to the CDI, the CDI output, and the signal at the tach.

Yamaha terminology is confusing. The computer on the motor is referred to as a CDI. However, it appears to have a transistorized ignition system and not a capacitive discharge ignition system. I say this because there is no charge coil in the stator assembly. Only a lighting coil and pulser coils.

It appears that the tachometer signal wire comes from the CDI via a blue wire that is in a four pin connector. The blue wire changes to a green wire that connects to the ten pin connector and then runs up to the helm for a connection to the tachometer. This is what the wiring diagram in the service manual shows anyway.

A pink wire to a Yamaha multifunction tachometer is normally used for the trim sender signal.

Yamaha does some crazy wiring stuff.
 
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