Mercury Alternator or voltage regulator question?

[drdetroit3]

I have a 1995 Ranger with a 125 2 stroke, I was having problems with the battery going dead at the end of a day of fishing, replaced the cranking battery, after a day of fishing, 2 fish finders on I an still having battery problems. At the end of the day when I start the motor both fish finder will turn off when I first crank the engine?
I checked the battery voltage with out the engine running 12.7 volts, after starting the battery the volts show 12.5. Sop the motor is not charging the battery.
Not a big motor guy but assume its the alternator or the voltage regulator? Not sure where these are or how to test, any advice would be great.

Thanks, Mike

 

[alldodge]

I would suggest start by looking closely at all connections. Make sure to bend the cables back and see if you see any corrosion under the insulation. Then clean all connections , which include the motor connector. My first thought would lean toward the ground side of the cables and connections

 

[mikeboston47]

check your spark plugs

 

[CharlieB]

There is no return on electrical parts. Test, test again, then test once more to make sure what you suspect is really defective before you buy any electrical part.

The stator has multiple sets of windings, only one set is used to charge the battery and that set is wired into the rectifier which changes the AC to DC for the battery. A bad diode and the battery dies.

Search this site for rectifier bench test. Disconnect the battery ground then remove the rectifier and test it with an Ohms meter. Make sure of your readings and compare to the directions.

Post your results so we can be sure what you find.

 

[drdetroit3]

What is a rectifier bench test?