How to test if motor is charging battery?

[dogtoter]

It often seems that after running the merc for a good hour or two, the battery (charged up before running and fairly new) will read 12.5 V (or a bit less) instead of the 12.65 V that would linger after a good overnite trickle and a few hours to come down from the 13+V of the charger.

Does this mean much? What voltage does a merc charge at? Is it possible my alternator isn't working? Is it easy to test (I am no electrician!)?

 

[arcrat]

Re: How to test if motor is charging battery?

13.5-14.5 ....test voltage reg if thats ok test stator... oktest batt then start motor and test again should show more voltage ... arcrat

 

[dogtoter]

Re: How to test if motor is charging battery?

The only thing I understand (and can locate on my own) is a test of the battery voltage while the motor is running. I will do this. If it is easy to locate the other test points, I would appreciate a description of where to put the V meter leads.

 

[dogtoter]

Re: How to test if motor is charging battery?

I seem to see no change, or even a slight bit less voltage (around 12.5 V) when the motor is running, whereas it was at 12.7 before and after the running.

I hooked up a disconnect terminal that I could switch off to isolate the motor hotwire from the battery after cranking it up. I took a read of the engine side of the hotwire and the ground terminal, and the wild floating V meter reads like there is no voltage.

I think it is safe to conclude the motor is not charging the battery. (At purchase, the lights and bilge pump were mis-wired at the dealer and all sorts of funny things happened until I simplified them.) And mabe related to this, the stator went out at the dock when the motor was only 3 yrs old and the dealer put in another, and I have always had a strong hunch that it has not been charging since then - for a decade!

We seldom use it for more than a few hours, and not too many stop/starts when we do run, so we have not been stranded.

Is it OK to run the motor knowing that it is not charging the starter battery? Is the battery needed for anything after startup?

What part is likely broken, and how do you access it?

All this time...

 

[dogtoter]

Re: How to test if motor is charging battery?

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[dogtoter]

Re: How to test if motor is charging battery?

I have searched and read a lot of iboat today, and here is what I think I know:

The stator needs a 12V battery to function properly, but not clear if it usres any amps, only employs the voltage field?

The rectifier is the likely culpret, and I have its pics below. If you can remove it w/o breaking something, there are a few quick readings w. a multimeter to see if it is shot. It is the transistor-looking thingy w/ a clear cover in the lower right of my exposed electronics.

If I am happy w/ keeping a fresh and charged battery to start the motor a few times on a two hour ride, can I just keep doing what I have unknowingly done for a long time?

 

[dogtoter]

Re: How to test if motor is charging battery?

Deleted