[jimwil3]

I have a 1996 Mariner 225EFI S/N OG319367 with an inop tach.

I replaced the tach with no help. Needle stays at zero. I've got good power and ground to tach. I've ohmed wires and no opens. The Teleflex troubleshooting chart says I should read around 3.5v AC from SEND to GND at idle. I've got zero. My regulator is in my alternator. But, one question is, where is my feed to the tach coming from? The stator or the regulator and what do I do next?

Thanks,
Jim

[j_martin]

I'm confused. Do you have a belt driven alternator?

If not, there are 2 voltage regulators that run off the stator. Each has a grey wire coming off it. One is connected through the harness to the tach. You could move that wire over to the other regulator for testing.

Stator to reg wires are yellow. Reg to ignition are red.

If these 20 amp regulators fail, they drop the tach signal.

please fill out your profile. It helps to know where you're from.

hope it helps
John

[jimwil3]

It is a belt driven alternator.

I checked for shorts to ground in the wiring from the ECM to the tach. None found.

Resistance check of Stator wiring was also good per the Mercury manual reading around 1200 ohms.

Profile filled out.

Jim

[j_martin]

Hate to say it, but if the ECM is supposed to supply a tach signal, and it isn't..........

[jimwil3]

Yes, the tach signal is produced by the ign ECM based on the crankshaft position sensor input.

The crankshaft postion sensor has a good gap and ohmns (1200).

I think that leaves me with the unthinkable, a bad ign ECM.

[j_martin]

Originally Posted by jimwil3

Yes, the tach signal is produced by the ign ECM based on the crankshaft position sensor input.

The crankshaft postion sensor has a good gap and ohmns (1200).

I think that leaves me with the unthinkable, a bad ign ECM.

That's what I didn't want to have to say.