1988 mercury 2 stroke 70 hp overcharging

[Ophion32]

At first starting battery volts 13,75 then climbed to 16,2
We replaced the rectifier no change any suggestions?

 

[ondarvr]

The rectifier doesn't have an affect on the voltage, it just converts AC to DC, if you see 13.75 then its working correctly. The voltage regulator controls the voltage level, it should be in the 14.2 + range at high RPMs.

 

[Ophion32]

From the rectifier it goes directly to b+ on start solenoid I understand what the rectifier does but what regulates the charging?

 

[ondarvr]

I'm not sure what you mean by, "regulates the charging". The Voltage regulator (if your motor has one, not all do.) and rectifier get the DC voltage to the battery at the correct voltage, the battery will somewhat regulate the charging on it's own and only absorb the amps it needs, as long as the voltage isn't too high everything's fine. There is no other mechanism or electronics on this motor that is responsible for adjusting voltage or charging rate.

​If your motor doesn't have a regulator, or it's not working, then 16+ volts is normal, it's not great for the battery long term, so if you're running for hours you may want to turn on something that will drain off some of the power.

 

[Ophion32]

If there's nothing on the boat that draws a have i big load mostly cruiseing california delta
Is there something that could cut the voltage down to 13.5?

 

[GA_Boater]

You don't have a problem to fix. As said by ondarvr, the battery acts as a regulator. Millions of outboards at high RPM are running around pumping 16 volts into the battery with no ill results

The battery must be a wet cell battery that does need to to kept full and not allowed to dry out.

 

[Ophion32]

Thank you so much

 

[ondarvr]

If there's nothing on the boat that draws a have i big load mostly cruiseing california delta
Is there something that could cut the voltage down to 13.5?

​You don't want the voltage at 13.5, it typically needs to be between 14 and 15 for correct charging.