Tachometer Problems !!

[Joseignacio]

I have a 1998 Mercury 150 HP Offshore. My Tachometer goes all the way to the end and stays there as soon as the motor starts......
Also, my Temperature warning buzzer is not working......
Could all this be linked to something going wrong ??

 

[henrye718]

Re: Tachometer Problems !!

There is a box on the engine with 1 red 2 yellow sometimes 2 red and also one black (ground). Anyway there is a grey wire that is connected to that box this what goes to the tach and gives it the signal to move.

Cheack all your grounds since you are having multiple problems that are not really related.

 

[Joseignacio]

Re: Tachometer Problems !!

Thanks. I'm going to check for that grey wire on the back of the gauge.

 

[emilime75]

Re: Tachometer Problems !!

Thanks. I'm going to check for that grey wire on the back of the gauge.

I could be wrong, but I believe what Henrye718 was referring to is the voltage rectifier located on the engine. I am not sure about your 1998 model, but on older Mercs the tach gets its signal from the voltage rectifier, sometimes referred to as a voltage regulator. It is my understanding that the rectifiers go bad rather often so it would not be very unlikely that was your problem.

Something else to look into, considering your temp buzzer is not working, is your wiring either at the engine or at the control box. Again, I am not sure about your 1998 model, but my 77 Merc outboard has the tach connector on the front of the control box and that connects to the tach. And since the temp buzzer is also ignition related, your problem is likely to be in the wiring in the controlbox, engine, or somewhere in between.

Good luck. Hope this helps.

 

[j_martin]

Re: Tachometer Problems !!

The tach is, electronically, a pulse counter. High reading would have to be either a bad tach or noise on the sample wire. Noise comes from bad grounds, or bad connections.

It sounds like you have several problems in your wiring. It would be best to get the manufacturers service manual for that engine and trace out the suspected circuits to find the faults.

hope it helps
John

 

[henrye718]

Re: Tachometer Problems !!

I could be wrong, but I believe what Henrye718 was referring to is the voltage rectifier located on the engine. I am not sure about your 1998 model, but on older Mercs the tach gets its signal from the voltage rectifier, sometimes referred to as a voltage regulator.

I have a 1998 ob too its smaller but figured he has a true voltage regulator like mine. I hope so 1990s dont seem that old to me

 

[Joseignacio]

Re: Tachometer Problems !!

I found the solution for the problem. There is a knob that can be turned with a flat head screwdriver on the back of the Tachometer itself that needs to be turned while the motor is running. I turned it right and left and it started working fine again.
Thanks Carlos Sosa for the advise !

 

[MarshMan73]

Re: Tachometer Problems !!

Sounds like corrosion in the microswitch that you turned left and right. You cleaned it by moving it I guess. May want to spray a little electronics cleaner on it if it acts up again before turning it.
By the way you wouldn't happen to be Nacho form the A/C board?

 

[Joseignacio]

Re: Tachometer Problems !!

No Nacho !

Thanks for the tip...

 

[Marty Niner]

Re: Tachometer Problems !!

I would just like to jump in here if I could...
I have a 1993 200hp offshore Merc, and my tach is not working either.
The tach reads "1" (thousand) when the engine is off, but when I turn the key on, it drops to zero. When the engine is running, it still shows zero. It appears that the tach is getting power, but no signal. Any thoughts?
Thanks

 

[Marty Niner]

Re: Tachometer Problems !!

I tried replacing the tach with a new one, different make, and still it does not work.....

 

[Marty Niner]

Re: Tachometer Problems !!

If anyone is interested, the problem turned out to be the voltage regulator..D'oh! A little more pricey than a tach!