tachometer "sender"

[adruid]

Troubleshooting a tachometer on a 1984 Mercruiser 140 #6821548. Where is the tach. information sent from on the engine? The tachometer reads very erratically at times, and I am trying to figure out if both ends are making good contact. Most of the electrical problems found so far are due to age and corrosion on the engine side.
Thanks!

 

[Bondo]

Re: tachometer "sender"

Ayuh,.... Welcome Aboard,.... The tach don't have a Sender, it get's it's signal from the (-) post on the coil,.....

It'll be a grey wire, or should be,...

 

[alldodge]

Re: tachometer "sender"

Troubleshooting a tachometer on a 1984 Mercruiser 140 #6821548. Where is the tach. information sent from on the engine? The tachometer reads very erratically at times, and I am trying to figure out if both ends are making good contact. Most of the electrical problems found so far are due to age and corrosion on the engine side.
Thanks!

:welcome: to iboats

Check your connections on your coil as Bondo mentioned. If you can find the use of a hand held tach you could compare readings

 

[achris]

Re: tachometer "sender"

Erratic tacho could also be the condensor failing. Do a full ignition service (new plugs, points, condensor, rotor)....

 

[adruid]

Re: tachometer "sender"

Erratic tacho could also be the condensor failing. Do a full ignition service (new plugs, points, condensor, rotor)....

Found the gray wire. Thanks to all for responding!