Tach no workie

[ATLWakeDude]

Can anyone tell me where the tach pick up is on my boat? Everything is connected at the back of the gage (and I get hours), but no tach activity at all.
I figure something is disconnected or a broke wire somewhere but can't find it anywhere.


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[dom w. forte]

There should be 4 wires on the back of the tach, Im going to give you the most common colors that we see ,1 purple should have key power,2 black should be ground, 3 blue should be the light inside and 4 grey should be from the engine, if you have a digital volt ohm meter you can switch it to hertz and hook to the grey wire and with engine running it should increase in number as you excellerate, if it does the guage is bad if it doesnt you need to trace the wire back to the engine.

[IDBoating]

Many DMM's don't have a frequency function. If yours doesn't, you might still be able to fake it by switching to DC voltage and measuring the grey wire. Since the frequency of the pulses should go up with RPM, the effect will be to increase the net duty cycle of the pulse train. The front end of the DMM will have some degree of filtering, which can then give you an averaged voltage that should increase with RPM.

This is not guaranteed to work - there are a lot of variables - but it's something else to try if your DMM doesn't have a frequency counter function. Hope it helps.

[boardman74]

Have the same issue with mine. Digital hour meter in the tach works but the tach does not. When I talked with a factory service warranty guy he said the tach is the most common gauge to fail. He said 90% of the time its the gauge. I have lights and the hour meter works and registers increasing hours. I checked and cleaned all terminals and still nothing.

[ATLWakeDude]

I really don't "need" the tach indication. I feel pretty confident that I'm not going to overspeeed the engine. The one main reason that I am concerned is that I am experiencing a run quality issue and I am not sure if the tach indication is tied to the tach input for the ECM or if they are independent.
When the engine is running steady state it runs fine. The problem I am having is during dynamic throttle conditions (pulling up a boarder, maintaining wake, etc) where I get what I believe is a rich condition and the engine will "bog" down until it seems to catch up to the throttle position.
Any ideas what to check or if the rpm indication ties to the IAC position via the ECM?


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