Tacho Calibration

[Sniper]

Hi everyone. Got a question for you all. Is it possible to calibrate a tacho? I have a 50hp 4 stroke merc and at idle the tacho is reading just over 1000rpm. Its not reving that hard. At WOT, its reading well over 6000rpm, which the gauge goes up to. This motor, as far as I am lead to believe, is limited to 6000rpm, and a buzzer sounds as well, which is not happening. So I am thinking the tacho is way out. Any ideas???
Cheers
Billyboy

[gone_fishing]

you can calibrate most tachos
depending on what brand etc
you need to ring a specilist really
some are just switchs some require a process
all the best

[haggis]

Hey sniper when I picked up my new boat with yammie 4 on it
I had the same problem . took it back to dealers who changed one wire , just a case of un plugging one wire and fitting it to another on . they had set it up as a two stroke which is a diffrent setting so with a lot of rpms the boat was hardly
moving . best talk to your local outboard mechanic of your brand of motor .
cheers fae haggis .......................

[tunaticer]

I suppose it is dependant on how it gets it signal ie does it get the signal from the firing circuit or does it get it from an electromagnetic pulse from the flywheel or crankshaft? There are several designs of tacho out there as far as i know the ones that work off a firing circuit can have one of two settings four stroke or two stroke the other has to be calibrated to the sensitivity of the magnetic pulses.

[Sniper]

Thanks for all the input everyone. Have worked it out. On the back of the gauge there is a tiny hole with cal writen on it. Just by slightly adjusting this, it brought the tacho reading back withing spec. Now reads the corect idle speed and no longer goes way over 6000rpm at WOT. Thank god. lol
Cheers
Bill

[Sniper]

Thanks for all the input everyone. Have worked it out. On the back of the gauge there is a tiny hole with cal writen on it. Just by slightly adjusting this, it brought the tacho reading back withing spec. Now reads the corect idle speed and no longer goes way over 6000rpm at WOT. Thank god. lol
Cheers
Bill

[Chimo]

Sniper

Thats got to be simpler than changing props and all that other stuff heh?

Cheers
Chimo