50 horse 3 cylinder Mercury not charging

starkyb

Petty Officer 1st Class
Joined
Apr 21, 2007
Messages
217
After a three day trip my battery died on the third day. When running at WOT the battery only showed 11.8 or less volts. The tachometer only works intermittently but stopped working all together so I figured it was the stator. I disconnected the battery and checked the stator wires and got 700+ on the green/green-white set and 1.2 on the yellow. So I checked the rectifier and I got nothing with testing both ways. Both tests were administered while still on the motor. Question 1) Do the parts need to be detached from the motor? Question 2). Would a bad rectifier keep the tach from working? I believe the gray wire coming from the rectifier is going to the tach. Just want to make sure I tested them correctly before I start buying parts. Thanks
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
It would help if you ID'ed which 3 cylinder 50 horse Merc you have. They are all the same, only different.

I'm guessing your rectifier is fried. But you can't test any of that while still connected.
 

starkyb

Petty Officer 1st Class
Joined
Apr 21, 2007
Messages
217
Got the new rectifier in now the tach works and the battery is charging. Only thing I had to use an old battery I had sitting around because the original one wouldn’t crank it even after sitting on the charger for hours. Could a bad reg/rec kill a battery and could a weak battery cause the motor to idle rough or shut off which is what mine did when testing the new reg/rec?
 
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