79 merc 90hp not charging

Been out many times this season and just recently noticed that my battery has been around 11.8 and dropping over time and last night I almost didnt get her started. What would be causing my battery to not charge? I have heard that I need to check my rectifier. According to the manual, take an ohm meter and check out each side. Only one side of mine gave me anything on the meter, but my rectifier looked different then the one in the manual. Is it shot? Any advice?

Thanks!

Re: 79 merc 90hp not charging

Even under full throttle my battery is only reading 11.8 volts. What should the output be / what should my battery be reading? How do I test the diamond shaped type rectifier? Any help would be greatly appreciated. Thanks!

Re: 79 merc 90hp not charging

Testing Merc?s square rectifier

If you use an analog meter set it on the RX1000 scale.
If using a digital meter, set it on the diode symbol.

1. Disconnect the battery leads.
2. Disconnect all wires on the rectifier.
3. Connect the red test lead to ground and the black lead alternately to terminals A and C.
The meter should show continuity.
4. Connect the black lead to gound and the red lead alternately to terminals A and C.
The meter should not show continuity.
5. Connect the black lead to terminal B and the red lead alternately to terminals A and C.
The meter should show continuity.
6. Connect the red lead to terminal B and the black lead alternately to terminals A and C.
The meter should not show continuity.
7. Replace the rectifier if you do not get correct readings.

Re: 79 merc 90hp not charging

Thanks! Its shot, getting a new one shipped this week. Hopefully that will fix my problem.