1989 Mariner 75 HP - Tacho and Voltmeter fault, what does it mean?

[motleyfirecrue]

Hi All,

My 75 Mariner has developed a quirky problem an I would love some assistance please.

When i start to motor the voltmeter and tacho seam to work, but after a short period the Tacho stops working and drops to zero and doesn't work at all for the rest of the trip (regardless of restarts). Actually the last trip the tacho didn't work at all.

The voltmeter will read about 12 - 13v at idle, but when you speed up the needle continues to rise to 16 + volts. From there it max's out and doesn't respond to any changes in engine speed. Each time you start up it does the same thing.

I had heard that a faulty tacho meant that the rectifier was on the way out. So i replaced it 2 trips ago, and with a multi meter it reads about 14v at the battery terminals at idle. I have a feeling the not-so-old rectifier was working fine, but i never actually tested it :facepalm:.

So even with the new rectifier, the same faults are occuring. Its almost as if there is a build up of resistance shortly after start up causing this to happen.

Any adeas would be greatly appreciated.

Merry Christmas to all,

Pete

PS If anyone has access to manuals etc for this motor, i would be greatly appreciative of resources

 

[jeffersondodson561]

Re: 1989 Mariner 75 HP - Tacho and Voltmeter fault, what does it mean?

It is a rectifier/regulator correct? 16 volts does seem high but I have seen unregulated systems go close to that. Verify voltage with a voltmeter. Was the regulator new/used? Because if it was used you might have bought a bad one? As far as the tach it does get it's signal from the rectifier. If you have a test light hook up to the grey wire on the back of the tach while the engine is running and see if the light pulsating could be tach, make sure you know how to use a test light too.