Tach stopped working-gctid819620

[Rick_Kenyon]

2005 Bayliner 275 with 5.0 mpi mercruiser. Tach has been acting erratic the past few times out. Today worked fine for half the ride then quit altogether. I figured the wiring contacts were probably dirty so took the dash panel out, pulled wire connection off tach, sprayed with electronics parts cleaner, connections on back of tach all looked clean. Put it back together. Fired it up, no tach reading. Where is the connection/sensor on the distributor, coil, etc that provides the input signal to the tach? Need to check that next.

[floatyerboat]

On my tachs there are three wires. Gray is the signal wire, purple is ignition wire and the black is ground. The signal wire ( gray ) is wired to the negative post of the ignition coil.

I'd check that first. The little nuts that hold the clips together come loose every now and then. The ignition wire might also have come loose.

If you don't have the same wire colors then check the back of the tach. It should be stamped near each post.

[Rick_Kenyon]

Thanks. Wasn't sure how it was connected to the distributor, coil, etc. actually didn't remember it's been so long since I fooled with one. It is a 3 wire tach, so I'll check the coil connection next.

[Chief_Alen]

A bad connection and or tach. can and will play havoc with your engine.

On the back of the tach. was there settings for different cylinders ?

cycle that switch back and forth a few times,set to the amount of cylinders the engine has.

[Rick_Kenyon]

Took things apart again this morning. Checked connection at coil, pulled plug (3 wires in it) sprayed with electronics parts cleaner, reassembled. Pulled dash assembly again, disconnected tach wiring plug (3 wires in it also) sprayed again with electronic parts cleaner, sprayed cleaner into back of tach into vent hole, noticed connection sockets seemed a little enlarged. Pinched connectors smaller with needle nose piers, reassembled, started engine, everything works fine again. I suspect that the wire sockets in the tach plug were just too loose to maintain a good connection. 12 year old boat, things expand and get worn. Tach has settings for the number of wires in the harness, 1 through 5. Tach is set on 3 wire setting.

Thanks to all for your ideas and help.

[Chief_Alen]

Now go boating .... enjoy !

[Rick_Kenyon]

Heading out today which is why I wanted to fix the tach. Thanks again to all

[floatyerboat]

I like those cheap fixes. Speaking of cheap those old tachs I have are totally made of plastic and have stamped in the back in ink, for 8 cylinder engines only.