question about RPM Guage...

[bebeard]

hi all,

I am trying to determine if my RPM gauge is bad....
When I have the motor off, key in or out of the ignition,
the RPM gauge sits at 1000 rpm? would that mean that is bad? can it be calibrated?

Thanks,

Brook

[boater]

where does it sit at an idle
where it sits with no power to it might not make a difference I think it needs owder to operate right at least I would check it that way before replaceing

[bebeard]

hello,

I will check the Idle run on the gauge and let you know..

Brook

[1FASTLASER]

When at rest all tachs that I have been associated with except for the very finest tachs usually sit at around 100-200 when no power is there. Turn the key on and needle should drop to 0 then register rpm's when started up. If it doesnt act in that manner find a shop close by that has a digital infrared tach and borrow or have them check yours for accuracy.

[carolina-rig-01]

Originally Posted by 1FASTLASER

When at rest all tachs that I have been associated with except for the very finest tachs usually sit at around 100-200 when no power is there. Turn the key on and needle should drop to 0 then register rpm's when started up. If it doesnt act in that manner find a shop close by that has a digital infrared tach and borrow or have them check yours for accuracy.

i asked my boat dealership about my tach doing this same thing. the owner told me that it was showing how many rpms the motor was turning when i shut the motor off, and when i turned key on it would drop to zero until started again (which it does). is he right about it showing the rpms the motor was turning before shutting it off or was he like most boat dealers and full of crap?

[1FASTLASER]

I'll be honest with ya bud I am leaning more towards being full of it....extremely full of it. Look at it this way...........when you turn your key on and not start it it drops to zero right............now turn the key off and wait a few seconds or if you want wait 10 minutes or days even,
most tachs will come back to that somehwere between 800 and 1000 to as much as 2000 rpm's. I promise you there is NO memory built into these tachs. The $50 and the $500 tacks all do the same. The ONLY tachs that I have seen do anything different is the ones that are used for racing with the tattle tale feature. and then you half to flip a switch to get the feature to activate the last rpm's the engine turned before you turned the motor off or blew it.

But this has raised an interesting issue in my mind and I will find some sort of an answer for those that want to know. It has never come across my mind or asked before that I can remember. Tachs have always done it so I accepted it and never gave it a second thought. I will try and shake out an answer.