Tach works intermittently

[pcrussell50]

2000 90hp Mercaha FourStroke... Stock recreational/fishmotor

Motor runs great. But for some ​reason, the tach only operates at or near idle, and even at that, sometimes not at all.

I'm inclined to think I need a new tach, since whatever is driving the tach is not causing to motor to run poorly... But that would be a total guess.

I want to have a working tach again especially since this pig is propped for holeshot, not speed and since it's a four stroke it likes a little more rpm... But I don't want to overrev it either. So I want a working tach.

-Peter

[bullet20vee]

There should be a small dial for pole settings on the back of the tach. Look what number it is set on now, turn the dial up and down several times and return it back to the original setting and try it out. I have had them start doing that too and sometimes that will fix the problem. Also check the wiring connections on the tach and the grounds on the motor.

[pcrussell50]

Thanks mate. I'll swing pole switch around here and there and see if that helps before I sink money into a new tach.

-Peter

[pcrussell50]

Here's a related question...

The tach pole switch is set at 6p. That's probably where it's always been since I got it back in 2011. For whatever reason, I just assumed that's the right setting. I just took a quick scan through the factory service manual though, and it doesn't say (unless I missed it), what setting to set your tach to.

What's the right way to find out?

2000 Merc 90hp FourStroke

-Peter

[RSWORDS]

Here's a related question...

The tach pole switch is set at 6p. That's probably where it's always been since I got it back in 2011. For whatever reason, I just assumed that's the right setting. I just took a quick scan through the factory service manual though, and it doesn't say (unless I missed it), what setting to set your tach to.

What's the right way to find out?

2000 Merc 90hp FourStroke

-Peter

To verify tach accuracy

1. Get out your timing light
2. Aquire a stop watch
3. Hook timing light to #1 cyl
4. Either hook flushing adaptor to motor or put boat in the water.
5. Start and idle motor
6. start stopwatch
7. count timing light flashes REALLY fast for one minute

*Note* in absence of a timing light you can just hold onto #1 plug wire with a wet hand. Although this method​ has shown to make it harder to keep track of your count.






But to answer you question, yes 6P is the correct setting. Lol