1988 Mercury 35 HP won't charge

[seaberry]

Checked resistance of coil and replace rectifier. Output voltage at the rectifier is about 4V at idle and goes up to about 8 V at 2000 rpm. Thinking about changing coil. Can i get flywheel off with gear puller?

 

[Laddies]

Re: 1988 Mercury 35 HP won't charge

Yes, you will need the proper puller. Before changing the stator test it yellow to yellow wire (disconnected) at the rectifier any reading is OK. Most charging problems are caused by the rectifier shorting to ground or an open diode

 

[seaberry]

Re: 1988 Mercury 35 HP won't charge

Thanks for prompt reply. I did get .65 ohm reading on stator. I replaced the rectifier because original did not pass continuity test specified in service manual. New rectifier did not pass either. I might be doing test incorrectly. Also, yellow and grey wires are reversed on the rectifier according to diagram in manual; would that make a difference?

 

[WillyBWright]

Re: 1988 Mercury 35 HP won't charge

The gray wire is just a sensor wire for the tach. It can be connected to either yellow wire. But try disconnecting it. If it's shorted to ground, it'll kill the charging system.

When stators fail, they will typically dead-short to ground or leave you with no continuity.

Go up to the FAQs. There is a rectifier test procedure up there.

When testing output, everything has to be connected. It'll only work if the electricity has someplace to go, like the battery. Look for battery voltage to rise with RPMs, say from 12.5v at idle to 13.2v at high idle for example. (don't take those figures literally)

Rectifiers usually fail from loose, corrroded, or crossed battery connections. Disconnecting the battery while the motor is running will cause them to fail too.

 

[seaberry]

Re: 1988 Mercury 35 HP won't charge

Battery was fully charged, therefore required no charge. I will keep an eye on it. Thanks for all the help.