2005 Signature Edition EX330 dead tach signal

[Mikeski]

So this is a new one and it has me a bit stumped. As a former electrician and electrical engineer there is not much electrical that gets to me but this one does has me stumped for the moment.

In December when I pulled my boat off the trailer to get some service work done I noticed the tach was not working. Since I was there only to pull the boat off the trailer I did not give it much thought other than to remember that I might need to address the issue in the spring. Well, I took the boat out yesterday and sure enough the tach signal is dead. I have 3 devices connected to the tach signal wire, the tach, the perfect pass, and my revolution audio volume device. None of the 3 work. So today I pulled the dash apart expecting to find something shorted in one of the signal wires and I found nothing. All of the wires look perfect, I isolated the tach and it still did not respond.

This is a signature edition boat so there is a gray wire coming directly from the motor harness connection up to 12 pin up at the dash. Both connectors at the motor and the dash look perfect. I don't have a scope or signal generator at home so I could not do too much besides look at the connectors and scratch my head.

If somebody was describing this problem to me the first thing I would ask is what was going on when the problem started. Unfortunately I believe everything worked fine up to the point when I was pulling it off the trailer to work on the trailer. Along the way I did change my 2 stereo batteries and they did draw a healthy arc when I hooked the power wires back up but this has happened a few times before without causing any issues.

Also unfortunately I sold the spare MEFI 4b controller that I had in my drawer for 2 years. If I still had that I would pop it in and see if is a faulty controller.

Suggestions?

Time to start going through motor wiring diagrams...

[Mikeski]

Update...

I bought a cheapie analog tach and tested the wire coming directly off the main harness at the boat. It is dead so the signal coming from the motor is dead. As far as I can tell this signal comes directly off the MEFI 4B motor controller so I am very concerned now.

[Mikeski]

More info, found the much needed PCM MEFI 4/4b diagnostic manual here: http://www.pirate4x4.com/tech/billav...(L510005P).pdf

Jeff should add this to PN reference section.

[Mikeski]

Official diagnosis is dead tach signal coming from the MEFI 4b engine control module. Temporary solution is to pull a signal off the coil trigger wire. At some point I hope to come across a cheap used MEFI 4b control module from somebody that has upgraded their ski nautique to drive by wire MEFI 5 so they can run zero off. Until then the coil trigger bypass will remain in place.

[Mikeski]

Temporary solution has been validated.

Message received from PCM tech:
"As you know the tach signal was always taken from the coil in the past. You are good with that work around. The MEFI has been known to have that particular failure in some cases."

[TRDon]

The first thing that comes to mind is the gateway is shot. Same thing happened to me. I lost half of my gauges but everything still ran. If you have a serial bus cable jumpered to each gauge, than they are individual addressed in the gateway to each unit and it disperses the signal. Im assuming that is what you are talking about with the mefi thing.

[Mikeski]

Signature Edition = no gateway

PCM confirmed this issue has been experienced before and my solution will not cause any issues.

[mofish]

I am having the same problem. My rotor came unscrewed while the engine was running. The tach went crazy and has been working intermittently since. I only get 3.5 volts at the tach gray wire with the key on, and about 1.75v with the engine running. The other engine (tach works normally) gets 7.5v and 3.75v respectively. They both measure about 11v at the coil gray wire

Did you splice into the gray wire at the coil for your trigger signal? I am thinking I should disconnect the gray wire at the tach and run a new wire from the gray coil wire.

I have two 2007 Marine Power 5.7L with MEFI 4 ECM's.

[bionaraq]

Man, I really wish Mikeski had done a how to on bypassing the signal. As a dumb mechanical engineer, it's all greek (letters) to me.

Though my issue is only the tachometer dead in my 2004 signature. perfect pass still works. I'll check around under the dash as it only started after i pulled the dash out to get the clarion remote out for a depth gauge.

[Mikeski]

You are in luck, I'm still around and I still own the boat.

There is a wire in the main engine harness you will need to tap into. Run the wire from the engine to the dash, then replace the signal to the Faria speedo and the Perfect Pass.

I'm changing the oil and installing the Nautic Logic GPS speed transmitter tonight so I can take photos and show you what wires you need and where they go.

I also sent you a personal message.

If others need this info feel free to email me at mikeskiw at gmail.

Happy Boating!

[Mikeski]

Here's the how-to cheap fix for a failed tach signal. I also confirmed on the MEFI4b wiring diagram that it is the pink wire.
https://youtube.com/shorts/ThbHddwO6r8?feature=share