Tach not reading

[NCSeaChaser]

I have a 2004 225 four stroke, and the rather cheap original tach is not working (although it does light up). The mechanic advised that it is not receiving a signal from the ECU and the only solution is to replace the ECU for ~$1,200. He advises that it is not possible to take an old-school reading from the alternator. Is this correct - replacing the ECU the only option? Thank you for considering this problem.

[boats.net]

If not getting a tach signal out of ECU then would be best to replace it.

[robert graham]

I'd double check your tach and wiring Before replacing a $1200 ECU! remove, clean and tighten all tach wiring and fuse(in-line or block), often humid marine environment and vibration will cause these circuits to lose connections. Find that small slot-head pole screw on the back of the tach and move it back and forth several times, then return to it's present setting. Your tach may be bad, maybe borrow one that you know works and install in your boat to check. New tachs are about $75, and they have been known to die after a few years! Good Luck!

[NCSeaChaser]

Thanks for the replies. As the mechanic said there was no tach signal output from the ECU, it would seem the condition of the tach and everything leading to it would be of secondary concern. How hard is it to verify the lack of a signal from the ECU? Is it possible he is incorrect about that and the problem does in fact lie in the tach or wiring? Thanks!

[robert graham]

I'm not saying your mechanic is lying Or mistaken, but I believe a lot more tachs fail than ECU units and I'd sure want to be sure before unloading $1500+labor for a new ECU. Just check your tach and wiring first. Good Luck and let us know what you find out!

[NCSeaChaser]

Just wanted to put a fresh reply out to see if anyone new had an opinion on this. If there is no tach output from the ECU, is there any option for getting a working tach other than replacing the ECU? Any creative ideas welcome and appreciated. Thanks.

[99yam40]

Seems like someone would be able to tell you what kind of output the ECU sends to the tach on that motor.

The normal style of tach for alternator powered ones count the pulses , and are not something you can measure with a meter to get RPM. And I have no idea what you would expect from the ECU either.

May be best to just hook up a known good tach to see if there is a signal and hook you tach to a different boat motor to see if it will read on it. That should tell you what is going on.

I have heard of something called tiny tach that you hook up to #1 plug wire to get a RPM reading, but have no idea if it works well on a motor like yours or not. But that is the only other option if your ECU is the problem, that I can think of

[boats.net]

Might could splice into the green wire from alternator and get a tach signal for tach but never tried it on the newer motors.

[throrope]

If your outboard runs as before, getting me to buy a new ECM would be a tough sell. My tach was giving me grief some time ago. I stumbled upon a white paper that flatly stated the most common issue with tachs is a bad connection. After reading that, some wiggling and a couple shots of WD40 under the console, I've long since forgotten about the problem.

Good luck and keep us posted.