Battery Wont Charge - 1979 Mercury 115 hp distributor model

[cairngorms]

hi,

My battery wont charge when the motor is running - Any ideas Rectifier possibly)?

Also I discovered milky oil in the lower unit, no signs of any cracks etc.The motor otherwise runs fine.

Would appreciate any assistance with any of the above, plus where to get parts, etc

Thanks P

 

[dwco5051]

Re: Battery Wont Charge - 1979 Mercury 115 hp distributor model

These old Mercs are great motors but they have a reputation for the wire insulation to become brittle over time. If it was mine the first thing I would do is pull out the wiring diagram and check for resistance or open circuts in all the wiring circuts. A break in the insulation will permit water to enter and corrosion of the wire itself. It will also give you a chance to check for loose or corroded connections. It may well be a bad rectifier or stator but before you spend money on new parts be sure that is the problem. Don't forget to check the plug between the the external wiring harness and the motor for corrosion. I am assuming that you have checked the voltage at the battery while the motor is running and you have a known good battery.

 

[cairngorms]

Re: Battery Wont Charge - 1979 Mercury 115 hp distributor model

Okay - Rhanks for the prompt response, I'll check out the wiring as suggested, and yes the battery is fine.

Any thoughts on milky gearbox oil? i changed the impeller, but not all the gaskets, do you think this could be the problem?

Thanks again.

 

[impatico]

Re: Battery Wont Charge - 1979 Mercury 115 hp distributor model

could be a water pump housing gasket or a seal somewhere. definitely water in the lower unit. when was the last time you changed the oil in there?

as for the charging system, get out the multimeter and check to see where your current ends.

 

[Chris1956]

Re: Battery Wont Charge - 1979 Mercury 115 hp distributor model

That motor has a two wire stator. Put a voltmeter on the terminal block about 1/2 way down the starboard side of the motor. The two yellow wires that are on that terminal block should have some AC voltage on them is the stator is good and the motor is idling. First diisconect the two wires that go to the rectifier, in case it is shorted to ground. If you see the AC voltage, it is likely the rectifier is bad, or the wiring is bad.

Those gearcases can leak at the prop seal, fill and drain plugs, driveshaft seals and shift shaft seals. I would replace the water pump base and seal as well as the plug gaskets and see if that fixes it. Clean the driveshaft with sandpaper, and lube it up before installing the new waterpump base and Oring.

 

[cairngorms]

Re: Battery Wont Charge - 1979 Mercury 115 hp distributor model

Thanks great responses - I will let you know how I get on.

thanks again P