Metering battery voltage. Help?

[DJ_Allatoona]

So, my new thing is a switch and USB port panel that I installed a few days ago. It has a voltmeter on it.
It works great, but I'm super dumb about metering voltage.
So please briefly explain something to me.
On the trailer, motor off, just sitting there, the meter reads 13.0.
Motor running, it reads from 17.0 to 17.4.
So when the motor is running it's reading the voltage from the motor, right? Like from the rectifier?
Like I said. Not a smart guy here. What do these numbers mean?

 

[sam am I]

On the trailer, motor off, just sitting there, the meter reads 13.0.

Sounds about right if motor was just shut off, should go down little further overnight to 12.4V/12.5V

Motor running, it reads from 17.0 to 17.4.

Something in wrong, that's too high. Double check that reading again with a different meter, if both readings agree AND you have a regulated system, it is most likely toasted. If you run an un-reg'd system, that sounds about right as well.

So when the motor is running it's reading the voltage from the motor, right? Like from the rectifier?

Yes

 

[DJ_Allatoona]

Something in wrong, that's too high. Double check that reading again with a different meter, if both readings agree AND you have a regulated system, it is most likely toasted. If you run an un-reg'd system, that sounds about right as well.

Appreciate the reply. Funny you mention that's too high, because sometimes my fish/depth finder (Garmin 160 Blue) will display a warning that says "Battery Voltage High" and will shut off. Only does it a couple of times a year, and always when I'm running. And I don't know if I have a regulated system or not. Motor is a Mercury 75HP made in 1986. Serial 0A984714. How do I find that out?

**EDIT** I just went through my SELOC book and I don't see any mention of whether my system is regulated, and no mention at all of a voltage regulator. And I see voltage regulators for sale for my motor, but for serial numbers starting with 0A996142. So maybe mine is one of the last ones without a regulator...?

 

[sam am I]

Good chance it is un-reg'd then. If your battery is aging a bit, the voltage will tend to creep up more and more with time. New batt might hold it down more towards 16'ish volts.

Could also add a reg like this, they do around 20 amps and will run air cooled, might be able to find a spot under the hood on the engine somewhere's it'll fit on.

 

[DJ_Allatoona]

Could also add a reg like this, they do around 20 amps and will run air cooled, might be able to find a spot under the hood on the engine somewhere's it'll fit on.

I can ADD a voltage regulator if I don't have one already? I wouldn't know where to connect all those leads.

And one more thing: in researching this problem, I found other guys who said they had weird electrical spikes because their stators were bad. I have some other 'bad stator' symptoms as well (occasional mystery stalls, hard restarts, wonky idle). I'm now strongly thinking that if I pop in a new stator, my electric headaches might go away. Thoughts?

 

[sam am I]

I can ADD a voltage regulator if I don't have one already?

Yes

I wouldn't know where to connect all those leads.

OldNew

in researching this problem

What problem? w/o a reg, that high voltage is normal. The Garmin shutting off is relatively a standard when it sees excessive supply voltage. In reg'd systems a bad reg flaking in and out will almost always spike the voltage but, flaky stator and stator connections and the like could also I suppose............

Those other most resent issues you just mentioned

occasional mystery stalls, hard restarts, wonky idle

all sound like typical engine issues, carb, flooding, idle mix, etc