Tachometer, the needle floats when at idle.

[ddbyrd3]

2002 Glastron GX 205 w/ a 5.0GL-B motor.

I have noticed lately my tach is floating when at idle, it floats anywhere from idle RPM to 4K RPM and back at forth. It does not do it all the time, but often enough.

Lastly, is putting a digital timing light on spark plug lead #1 and reading the RPM a valid method to verify tach RPM reading???

 

[Scott Danforth]

reach under the dash, move the tach selector switch back and forth a few times, then put back where it was.

yes on the verification.

 

[ddbyrd3]

I will move the selector switch back and forth.

With regard to the digital timing light on #1 spark plug. At the end of last season, I connected my timing light and laid it on the rear seat. Hot lapped the boat back and forth and noticed my timing light read about 400 RPM lower than my tach.

What is the best way to assure my tach is accurate??

 

[Maclin]

I would say you already did one of the best ways

 

[Bondo]

Ayuh,..... That's exactly how I cross-check a dash tach,.....

I trust my timin' light to be accurate,.....