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Tach not working

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mike@holden

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I have 2002 F225txra. Tachometer issue has stumped me. I replaced old tachometer because it kept going out after voltage would go over 14 volts. I installed Faria gauge. Now I get nothing, 0 rpms. I hooked up gauge to another boat and it worked correctly, on setting 5 for 12 pole alternator. I went and checked 10 pin main harness all good there. I back probed green wire from ecm. I get around .3 volts AC. I checked diodes on rectifier all seem good. I hooked up tachometer at engine by back probing wires, still 0 rpms. I do not know where to go from ecm to figure why it is not outputting tach signal. I hooked up engine to laptop. It is showing it reading rev/m. I always noticed motor always seems to charge high like 14.5 volts. Anyone have ideas?

Thanks
 
14.5 volts for that model is not excessive.

Rectifier is not in the loop with respect to the tachometer signal for that model motor.

If you are able to test the green wire from the ECM for voltage why not test it for frequency? The tachometer is looking for a frequency not a voltage.
 
I will need to get a multi meter that reads hz. I hooked up the faria tach back probed green wire at ecm and probed 12 + and 12 - at main 10 pin. Tachometer still at zero. This new tach hooked up to another outboard and it worked fine. Is tach signal loss common on older 225s ecms?
 
No, the loss of a tachometer signal is not common. At all.

If YDIS is displaying RPM then the ECM is getting the message. Why you are not seeing that on the green tachometer wire is the mystery. The fact that you are seeing voltage on the green wire is indicative of something.

I would go back and disconnect, inspect, clean and reconnect all of the electrical connectors that are the loop.
 
I decided to splice into stator wire and green wire at the main 10 pin connector. The tachometer is working in that configuration. So I know now nothing to do with wires from dash to 10 pin. I may pull trigger on a used ecm to see if that is issue. I am doing all this while boat is on lift over water. What fun!
 
You can run the motor with the ten pin harness disconnected. I would do that with the tachometer connected to the green wire in the main engine harness to see if it now works or does not.
 
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