Tachometer acting funny! Please advise

[Bilgamesh]

I have a 3.0 L mercruiser that has been recently rebuilt, so I am sensitive to revving too high. Today, my tach was clearly reading way too high for 30 minutes or so. In other words, the engine was revving about 1500, but the tach was reading 3000. It eventually went back to normal after a couple times of stopping and shutting down. I want to be cautious, so I will appreciate any ideas?

 

[maxxman04]

Re: Tachometer acting funny! Please advise

check wiring connections at motor and helm. check wires in between for cracking/splitting/chaffing.

 

[arks]

Re: Tachometer acting funny! Please advise

Yeah, probably a poor ground.

 

[ScarabSprint]

Re: Tachometer acting funny! Please advise

Where does the tach wire connect to on the 3.0 liter?? Pictures would be great. Thanks

 

[maxxman04]

Re: Tachometer acting funny! Please advise

tach wire comes off the coil. may be gray or gray with a different color stripe. possibly solid green wire as well. bit hard to say without. but usually it's one of the wires on the - side of your coil. however this is general info, a manual for your year motor would show this.

 

[rbh]

Re: Tachometer acting funny! Please advise

hey there hows your night going-
I seem to be running into gauge problems myself and what I have been doing to correct them is checking all the connection points and cleaning them as well as replaceing all the push together/eye connectors, as our boat is 24 years old and the connecters have both corrosion issues and they have lost their grip (not a good tight fit-griptivity)
if you have to pull out your gauges check them all.
try alittle dielectrical grease
rob

 

[gadget73]

Re: Tachometer acting funny! Please advise

Try a bit of percussive maintenance to the top of the dashboard. One of my tachs reads really high every time I fire the motor, a good thump on the top of the dash settles it and it will remain fine until the next startup. Not a clue why it does that, I've cleaned and tightened and fiddled and faddled with every connection behind the dash and at the motor. Its been like that for 8 years now with no change. I've learned to live with it.

 

[Bilgamesh]

Re: Tachometer acting funny! Please advise

I am getting near-sighted these days, but I believe I located a tiny dial or knob on the back of the Tach. Presumably this is the one that switches between 4 and 6 cyl. I could not turn it with my finger because it was so small. I did jiggle it a little, and performed the recommended percussive maintenance to the face, and voila, the wacky tach is back to normal, at least for now. - Thanks!