Tachometer issues

[mrfishaholic]

Ok, I was having tach issues in which necessitated me purchasing a new tach in order to have a functioning tach. I purchased a Merc (quicksilver) tach that has several settings on the back. I have a 1990 75HP Merc. I dont know which setting I am supposed to have it on as there is not a 3 cyl setting. there is a 2cyl, 4cyl, 6cyl and 2 additional P settings. One dealer says it should be at the 6cyl setting, the other says the 6P setting. I have tried both and have further problems.

the needle on the tach keeps pulsating though the engine is not reving above an idle. the pulse ranges from 0 rpm to 4000 rpm sometimes fast sometimes slower, but the needle is bouncing as though it is not getting an accurate reading. It is NOT smooth.

With the ignition in the on position, with the motor not running, I am getting a slight pulsation of 0-200rpm as well.

Thanks for the help.

 

[Texasmark]

Re: Tachometer issues

I just installed a Quicksilver tach on the son's V6 and it said to set it to 12P. So since you are running a 3 cyl I'd assume 6P is correct. I am running a 3 cyl engine but don't know what number my tach is set to....guess I could crawl under the dash and look.

I don't like what you said about bouncing around. I don't know the circuitry in the tach, but by what they put on the back the tach merely counts pulses (sine or half sine waves) from the stator via the rectifier/regulator.

If you dialed in the wrong number the needle won't be sitting in the correct position for a given number of pulses counted (engine rpm)......should have nothing to do with bouncing around unless it bounces if you select too low a number(like 2P on a 3 cyl engine) and the needle pegs out. I don't know what would happen then.

You may have a bad rect/regl which will cause erratic tach operation. What's your battery voltage at 2000 ish rpm's.....assuming battery is fully charged?

Mark

 

[jmburock]

Re: Tachometer issues

I just put in a Quicksilver QSS Tach on my 89 Mariner 3 cylinder 75hp. It is 12 pole/ 6 pulse for the setting. hope that helps.