93 150 Tach Problems Wiring Diagram

[lpwhaler]

I have a 1993 Yamaha 150 and my tach quit working. I have the Yamaha digital gauges and all I am getting on the gauge is a zero. I replaced the gauge with a known good one and I get the same thing. Looked around under my console and don't see any problems. Where does the rpm signal come from on the engine? I wanted to go back there and follow it back to the gauge. Has anyone had a similar problem? Is there anywhere online I can get a wiring diagram?
Any help would be greatly appreciated.
Thanks,
lpwhaler

[boscoe99]

The signal for the tachometer comes from the CDI via the ten pin harness.

You can do a continuity check of the ten pin harness from the connector at the helm to the connector on the motor. If good continuity there, then check the main engine harness for continuity from the engine ten pin connector to the connector at the CDI.

[lpwhaler]

93 Yamaha 150 Tach Problems, Wiring Diagram

Thanks for the help Boscoe99,
How do I determine which pin it is? Or the color of the wire?
Someone told me it was a green wire, problem is there is three green wires going to that gauge unit and at least four green wires in the harness.
Can the engine still run with a CDI that is not sending a tach signal?

[boscoe99]

Sorry, it is the green wire.

There are only two green wires in the harness. Grass green for the down trim signal and a darker green for the tachometer.

Yes, a cdi can still operate even if the tachometer signal is not being outputted.

[boscoe99]

What type of throttle/shift do you have? 703 side mount with integral switch or 704 top mount with separate key switch

What is the exact model of you motor?

[lpwhaler]

93 150 Tach Problems Wiring Diagram

I have a Model 704 Top Mount with a separate key switch.
My engine is a Model 1993 150TLRR
The serial numbers are 6G4 L 407664.
Thanks much for you hanging in there with the help.
Carter

[boscoe99]

See illustration below. One green wire for the tachometer signal. Starts at the CDI and runs in the engine harness to the motor side ten pin connector. Runs up the ten pin harness to the connector that goes to the key switch. From the key switch it goes to the tachometer green wire lead via the small fused harness.

You can remove the CDI connector and the ten pin connector to do a continuity check of the engine harness. Then check continuity of the green wire from the main harness ten pin connector to the key switch, through the fused harness and then on to the tachometer.

[lpwhaler]

93 150 Tach Problems Wiring Diagram

Thanks Boscoe for the wiring diagram.
It looks like my CDI is bad. Just my luck..
I isolated everything piece by piece and I have continuity from CDI to the gauge.
Is there a way to see if the CDI is putting out a signal?
If I have to buy one where is the best price?
Thanks again,
Carter

[lpwhaler]

93 150 Tach Problems Wiring Diagram

I checked with my friendly neighborhood Yamaha Dealer on the price.
He only wants $965.00.

[boscoe99]

According to NADA the average retail value of a 1993 115TLRR is $1056.00. I would hesitate to pay $965.00 for a new CDI just to get a tachometer output. But, that is a personal call. Heck, some folks don't even have a tachometer installed.

What I might consider doing is performing a slight modification to the motor.

The tachometer signal generally comes from the lighting coil. It goes through the CDI, on to the wire harness and on to the tachometer.

I see no reason that you could not splice into a lighting coil output wire and then run that wire to the green wire. I would first disconnect the green wire from the electrical connector that attaches to the CDI. The lighting coil output frequency will be sent to the tachometer via the normal green wire and the tachometer should indicate the engine RPM.

Mr. Rodbolt - What are your thoughts on this matter?

[lpwhaler]

93 150 Tach Problems Wiring Diagram

Let me ask this, if the tach signal comes from the lighting coil and goes through the CDI could the lighting coil be the problem?
Is the lighting coil under the flywheel or where is it located? Will the engine run if it is bad? And how do I identify the lighting coil output wire?
I will try and bypass the CDI if I can find the lighting coil output wire.
Thanks again for all the help.

[boscoe99]

Now that I think about it some more, maybe it is not the lighting coil. Let me do some looking at some wiring diagrams and see what I can come up with. In the meantime, maybe Mr. Bolt will ring in.

The coils are all under the flywheel. Magnets in the flywheel wiz by the coils and do their magic.

[rodbolt17]

tach signal is generated by the CDI based on pulser coil input.

can be tested with a voltmeter .
check voltage at idle on the dark green wire to ground.
then as engine speed increases to about 2500 RPM you should see a linear rise in voltage.

CDI failure is incredibly rare.

[boscoe99]

Although a CDI failure is extremely rare, it can happen. If the OP confirms this, what are your thoughts about tapping into either a lighting coil lead or a pulser coil lead to pick up a signal for the tachometer? It might or might not work but I don't think any harm can come from this. If the motor were to run poorly then the electrical connection could be removed. This assumes that the CDI has already failed in the form of no tachometer signal output.

Might the lighting coil output voltage be too high?

I was basing my comments about the lighting coil on the following Yamaha verbiage. The reason why I questioned this fellows particular motor was because I could find no connection of the lighting coil output to the CDI. The output appears to go to the rectifier/regulator only.

The tachometer indicates engine speed by receiving pulses
directly from the lighting coil or from the CDI or computer.

[lpwhaler]

93 150 Tach Problems

I installed a known good CDI yesterday, and all my problems went away.
Thank you for the help Boscoe and rodbolt.