RPM Gauge

[Boilers2000]

Noticed my RPM gauge seems to be acting a little wonky. Two weekends ago read 5000 RPMs but throttle was 25%, then poof seemed to work right. This morning 3000 RPMs was crusing about 28 MPH, aligned with prop calls, 2 adults 3 kids on the boat...went to run back to the docks and 3200 RPMs was only showing 22 MPH. Conditions feel about the sam. Gauge will randomly mac out then appear to read correctly, and if I tap it it will mad and reset. No change in how the engine sounds when its acting weird, and trying to gauge where throttle is in the same position. Is it the gauge or something else? Its a 92 4.3 LX mercrusier engine. TIA, Happy and Safe 4th to everyone, Happy Boating!

 

[Rick Stephens]

Obviously you could just replace the tach. But cheaper first steps are clean the connection at the coil and the back of the tach. And while you are there cycle the switch on the back of the tach for a few moments that sets it for engine size. Look at it first, that switch will be pointing at the 6 cylinder engine location and may have a six next to it or a letter. Cycle it around and hopefully clear up and corrosion but make sure you go back to the same setting.

 

[achris]

'RPM gauge' is a tachometer, or 'tacho' for short. And yes, all the things Rick beat me to saying...

Chris....

 

[Boilers2000]

Tachometer, that's the word I was looking for. Thanks for the list of troubleshooting ideas. Happy 4th!

 

[RaceCarRich]

If tapping the tach has an effect, your problem is right there in the local area. Tach itself or wire connections immediately behind the tach. Perhaps exercising the switch as Rick suggested. No need to look at throttle position, engine compartment or anywhere else that can’t feel the tap.