# TACH READING TOO HIGH



## SeaHawk (Feb 12, 2008)

The last few boat trips the tach on my Suzuki DT140has displayed approx. 25% higher reading than usual. Motor runs fine, prop is fine, connections good, just can't seem to determine why the change. Anyone have an answer or experienced this before? Thanks


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## The Maintenance Shoppe (Nov 5, 2007)

Analog tach??? We can verify with different tachometer or stroboscope.


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## DOUBLE "D" & LV (Oct 2, 2007)

As a tach (nondigital) gets older, they sometimes will start to jump, stick, or read incorrectly. This is due to the moisture taking it's toll on them. Sometimes you can move the adjustment on the back of the tach around to make a new connection on the contacts. Do this while the engine is running. See if that will take care of it. If not, be aware of it and if it gets too bad, you will need to replace it. Before you do this, take a moment to verify what voltage the engine is charging at while it is running. If you do not have a volt gauge on the dash, then use a volt meter at the battery. If it is putting out more than around 16 volts, then your regulator is more than likely bad. This also runs the tach signal and in rare instances can cause a high tach reading. Hope this helps.


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## bfish (May 19, 2008)

mine does that and i tap on the gauge and it goes back to normal


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## KingMe!!! (Apr 25, 2008)

I had this going


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## KingMe!!! (Apr 25, 2008)

Don't know what happen there but i'll try this again.

I had this going on in my boat and there was a dial on the back of the gage that I had to turn while the motor was running at idle and bring it back down where it needed to be.


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## SeaHawk (Feb 12, 2008)

Thanks to everyonefor the advice.Hopefully I'llrepair or replaceit this weekend and confirm that there is no problem with the regulator. Thanks again..


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## Chapman5011 (Mar 7, 2013)

The Maintenance Shoppe said:


> Analog tach??? We can verify with different tachometer or stroboscope.


I was searching here for info regarding bad tachometers. I see an old thread here about it. 
I figured I would ask

Do tachometers go bad.
I have twin outboards. When at idle one runs a little less than 1000,maybe less, and the other tach , when I turn the key immediately jumps to 2000. As I cruise the motors are at the same tone meaning they should be about the same rpm's. The second tach always is running almost 2500 to 3000 rpm's more than the other. Sometimes when I turn the motors off, the tach that seems to be acting up still reads 1000 until I turn the key on then it will go back to zero, but when I crank it , it jumps up and double if not triple what the other tach is reading.
My question is will replacing the tach fix it or do I have major issues. 
Both motors run great
Sorry but you were the PFF member I chose to send this to in case you were wondering why I sent it to you. I think your screen name said the maintenance shop.
This was from a thread several years ago
Scott


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## The Maintenance Shoppe (Nov 5, 2007)

Tachometers do fail, either your tach is bad or the voltage regulator.


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## Chapman5011 (Mar 7, 2013)

The Maintenance Shoppe said:


> Tachometers do fail, either your tach is bad or the voltage regulator.


Replacing tach should be simple up grade. My center console will allow me to switch things out easily.
Replacing the voltage regulator....is that a major deal for a real mechanic or is that a DO it your self type fix. 
Just getting an idea what I'm into.
I will research more about the replacing of the voltage regulator.
Thanks in advance for the help.


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## X-Shark (Oct 3, 2007)

Parts swapping can get REAL expensive too. Have it checked.....Confirm the bad part....Replace THAT part.


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## murfpcola (Aug 28, 2012)

Just a thought.if I had twins I would swap the wires port and starboard and se if the problem moves or stays on the same tach. This would tell if tach or motor is the problem.


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## Chapman5011 (Mar 7, 2013)

I could just opposite the wires on the two tachs. They are simple to get to because of the center console. I may try that if it doesn't take to much effort. Other than that the boat runs fine. Just one tach is about 2500 - 3000 rpm's higher but both motors are running at the same tone if that makes since. One motor is not running harder than the other from what I hear. Just noticed it last time I was down . I never have really paid any attention to it before now.


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## X-Shark (Oct 3, 2007)

murfpcola said:


> Just a thought.if I had twins I would swap the wires port and starboard and se if the problem moves or stays on the same tach. This would tell if tach or motor is the problem.


What he said is exactly what I'd do. You already own the test parts.


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## Chapman5011 (Mar 7, 2013)

Edit
I was repeating what I said earlier


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## AndyS (Nov 22, 2011)

bfish said:


> mine does that and i tap on the gauge and it goes back to normal


When I was in the Army, back in the day, we used to refer to that as "_percussion maintenance_"


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