Tachometer reading less than 0

[Endeavor2bnc]

There are twin engines w dual techs. One tach is at zero and other is pegged low when engines are off. Is this a big issue and how can they be calibrated?

 

[joereeves]

You don't say what year/hp/make the engines are, nor the tachometer make, and you do not mention if both tachometers function properly when the engines are running, however.............

If the tachometer function properly when the engines are running, and to pick a figure when they're idling just before shutdown, the tachometers are reading say 850 rpm..... that reading should stay on the tachometers when you turn the key off, then when you turn the key back on, the reading should drop to zero. Under no circumstance should the reading drop under zero.

Assuming you have either V4, V6, or V8 outboard engines (Evinrude/Johnson), and the tachometers have a dial on the back of them, that dial should be set to number six (6).

Describe the antics that your tachometer is going thru if different than the above, and are they digital or analog?.

 

[Endeavor2bnc]

You don't say what year/hp/make the engines are, nor the tachometer make, and you do not mention if both tachometers function properly when the engines are running, however.............

If the tachometer function properly when the engines are running, and to pick a figure when they're idling just before shutdown, the tachometers are reading say 850 rpm..... that reading should stay on the tachometers when you turn the key off, then when you turn the key back on, the reading should drop to zero. Under no circumstance should the reading drop under zero.

Assuming you have either V4, V6, or V8 outboard engines (Evinrude/Johnson), and the tachometers have a dial on the back of them, that dial should be set to number six (6).

Describe the antics that your tachometer is going thru if different than the above, and are they digital or analog?.

They are twin 2004 Johnson 140 hp 4 stroke motors. When they are running, the one throttle is higher to get them at the same rpm. Currently we are out of the water for hull maintenance. The one tach reads 0 and the other is pegged low.

 

[Boobie]

You either have a tach that is bad or one mtr isn't running as good as the other. First thing to do would be to verify the tachs with a "shop tach".