Flaky Tacometer

[freedbill]

The tachometer on my Yanmar 3GMF has started jumping around a lot. It will hold steady and give good readings through about 1100 RPMS. Then, as I accelerate, it will start jumping between 0 and 2000 and never give a reliable reading again until I drop back to under 1100 RPMS. I have cleaned and checked the wiring and connections to no avail. I am now faced with replacing the sending unit ($100+) or the Tacometer ($200 +) or both.

Does anyone have any further troubleshoooting suggestions, to help me determine rather it is the sending unit or the tacometer or something else that needs replacing?

Many Thanks
Bill Ladd

[GordMay]

Try asking on the Diesel Clinic

http://www.dieselclinic.com/forums/

Diesel Clinic :: Index

Regards & luck
Gord

[freedbill]

Thanks for the reference! I have just joined and posted my question.

[svstrider]

Originally Posted by GordMay

Try asking on the Diesel Clinic

http://www.dieselclinic.com/forums/

Diesel Clinic :: Index

Regards & luck
Gord

Resurrecting this old thread as I have developed the same problem on the same engine. The engine does not rev and sounds normal. I tried to followed Gord's link but the site looks like it no longer exists.

Any suggestions would be appreciated.

[tager]

I'll be your tacometer. That's a job I definitely wouldn't flake out on. Eating tacos.

[waterworldly]

tach readings come from your alternator usually. Check the belt, it may be slipping a bit, usually when you don't use the boat for a bit, and you get some rust dust on the pulley, it will embed in the belt and cause some slippage. Usually you can tell by ear how many rpms you are doing.

[bill good]

so far it has been always wires connectors plugs & not the sender or tacho on my boat. The most troublesome was the connector to the sender which is now held on with self tapping screws. various bits of test gear can check the units like frequency meters & audio generators if you know somebody with the gear. A multimeter will do the job of finding the trouble. the circuit is in the owners hand book.

[sailorboy1]

may then this recently and is a pick-up sensor mounted to the flywheel, problem was a corroded wire at a harness connection

[Highlander40]

My Yanmars had a similar problem. The hour meter on one engine was off too.
The problem was the push-on connector on the back of the instrument cluster. Just squeeze the female side a bit until it goes on snugly.

[svstrider]

Thanks to all from the collective consciousness. I am off to squeeze into the engine bay for a play. I will update with my findings.

[svstrider]

Originally Posted by Don Lucas

may then this recently and is a pick-up sensor mounted to the flywheel, problem was a corroded wire at a harness connection

Don was correct - problems solved