850 mercury charging problem

[hereto]

I have a 1977 mercury 850 with ADI ignition. With the engine not running I get 12.5 volts at the battery. with the engine running I am now getting 13.2 volts at approx. 1500 rpms. I remember checking the voltage with engine running before and was getting something a bit over 14 volts. My tach does still work, can I rule out the rectifier? I have checked the battery with a hydrometer and it looks good, plan on having it tested with a load tomorrow.

Would greatly appreciate some help as what to check next. Thanks in advance.

hereto

 

[Faztbullet]

Re: 850 mercury charging problem

Sounds like its working as designed, the more the battery is charged the less the output as the battery is the regulator in this system.

 

[hereto]

Re: 850 mercury charging problem

Hi again all,
I found a simple test proceedure for checking the rectifier. My rectifier checked out bad ( both AC posts open ).
I replaced the rectifier with a Radio Shack rectifier that I had read about on this forum. My battery used to read around
14V with the engine running at 1500 rpms and the battery fully charged. After the rectifier died I was only getting 13.2
volts at 1500 RPM , now with the RS rectifier I am seeing 13.9 volts at same RPM ( actually don't see why I was getting
over 12.6 volts with the bad rectifier), but the problem seems to be solved. Hope this may help someone else out there.

hereto