Tach reading to high

[henrye718]

Tired of always having boats with tachs that dont work right I decided to fix this one.

I knew it was reading high from the sound of it and calculating the MPH speed along with the prop size. What I was not really sure if it was off during high RPMs and right at idle or not. So I ordered a Tiny tach hand held tach unit.

It turns out my true idle in neutral is 850, dash tach reads 1100-1200 It gets worse as the RPMs increase. 4500 is read as 6k by my tach.

I searched the forums for a good while, found no one with a solution to something like this. I would guess my options are to replace the tach or the rectifier? Any ideas?

Its set to 6p I did not find any lose connections. It has system check built in.

It seems alot of people have had this problem and were never able to fix it or never came back to report it.

Thanks for reading all.

 

[psteurer]

Re: Tach reading to high

You did not say what motor you have and the year of the motor. For a Teleflex tach, some 2 cylinder motors are set to 5P. All V models and 3 cylinders are set to 6P. Basically for a 2 stroke, you set it to 1/2 the number of alternator poles.

 

[petryshyn]

Re: Tach reading to high

Year? Model? Tach manufacturer?

 

[henrye718]

Re: Tach reading to high

Year? Model? Tach manufacturer?

2001, 2 stroke, 60 hp johnson, 3 cylinders, model: j60plsid.

Tach is made by OMC /w system check. This tach is original to the boat installed by the dealer. It worked right at some point im sure.

Oh and the charging system is working fine.

 

[Barnacle_Bill]

Re: Tach reading to high

6P is the correct setting. Move the setting back and forth several times then reset it again exactly on 6P. Close doesn't count. Those are very small contacts in there and sometimes it must be right on.

 

[henrye718]

Re: Tach reading to high

6P is the correct setting. Move the setting back and forth several times then reset it again exactly on 6P. Close doesn't count. Those are very small contacts in there and sometimes it must be right on.

Got it thanks I will try that.


Anyone know a place that services these or rebuilds them just incase, its discontinued and I would like to keep the matching gauges.

 

[henrye718]

Re: Tach reading to high

6P is the correct setting. Move the setting back and forth several times then reset it again exactly on 6P. Close doesn't count. Those are very small contacts in there and sometimes it must be right on.

I turned it back and forth a few times and placed it exactly on 6P, works good now. Thank you.

PS: it was set a few MM off of 6P when I first looked at it.

 

[petryshyn]

Re: Tach reading to high

Good catch bhile!!!