Melted rectifier.

[fincherjon@yahoo.com]

I finally got the old Johnson running and idling to satisfaction. When shut it down after making adjustments I noticed the rectifier was dripping down the engine. What should I be checking besides ground connections? Is this how they normally fail? 89 60hp

 

[Vic.S]

Battery connected with polarity reversed ??????

 

[fincherjon@yahoo.com]

I'm pretty sure it wasn't. I will check this evening.

 

[schematic]

I finally got the old Johnson running and idling to satisfaction. When shut it down after making adjustments I noticed the rectifier was dripping down the engine. What should I be checking besides ground connections? Is this how they normally fail? 89 60hp

you need to check the rectifier thoroughly for opens and shorts if you don't plan on replacing it....

 

[gm280]

Just speculating here, but if you were able to crank and have the engine start and run, I don't see battery cables being reversed myself. However, You easily could have had one or more of the diodes in the rectifier pack short and dump all the current through it to the battery or even a ground short condition. That would surely toast a rectifier. I just hope your stator is okay now. JMHO!

 

[fincherjon@yahoo.com]

The battery was connected correctly. I'm going to replace the rectifier. How can I tell if the stator was damaged? Symptoms? Thank you guys.

 

[F_R]

Visual check for burnt stator coils. Electrical resistance test with an Ohmmeter. Or just see if it still works.

99% of rectifiers fail because of loose, or corroded battery cable terminals. Or disconnecting them while the engine is running. If the cause is not corrected, you probably will blow a new rectifier. And yes, connecting the battery backwards will blow the rectifier instantly. You can't disconnect it fast enough to prevent that from happening. And clean those connections. Don't just look at them, clean them shiny bright.

 

[emdsapmgr]

FR hit the nail on the head. If the rectifier is shot, likely the tach will have quit working also.

 

[Crosbyman]

if it is just a rectifier (two phase) test with a new one from Radio shack....4 $ good for 25 amps
http://www.radioshack.com/25a-50v-full-wave-bridge-rectifiers/2761185.html

 

[gm280]

Before simply changing the rectifier, take a meter and check the wires that normal go to the battery to verify they are not shorted to ground any place. If they read open with reference to ground, then replace the rectifier and happy boating. Otherwise you will toast the new rectifier as well. JMHO!

 

[fincherjon@yahoo.com]

Thanks again. I'm going to replace the battery cables and rectifier. I wanted to water test the engine this weekend and I've read that I can run without the rectifier without harming anything. Is this true?

 

[schematic]

Yes its true. The stator will produce up to 60V. when open circuit. Well below the insulation capabilities...Just keep the wires isolated from each other.

 

[fincherjon@yahoo.com]

Forgive my ignorance but I don't know which wires you are referring to. If I remove the rectifier. The two yellow wires that the yellow wires of the rectifier piggy back on should stay connected as they are, correct?

 

[sutor623]

Forgive my ignorance but I don't know which wires you are referring to. If I remove the rectifier. The two yellow wires that the yellow wires of the rectifier piggy back on should stay connected as they are, correct?

Those yellow wires coming OFF of the stator need to be disconnected and taped up well. This will keep the charge from even hitting the rectifier at all. Just make sure your battery is topped off, and you wont be draining the start battery with any onboard electronics or starting your motor too many times during the day.

 

[Vic.S]

Forgive my ignorance but I don't know which wires you are referring to. If I remove the rectifier. The two yellow wires that the yellow wires of the rectifier piggy back on should stay connected as they are, correct?

Yes disconnect the rectifier leave all the other wires secured to the the terminal block in their original positions.

Far more sensible and safer to leave them secured like that than flapping about loose with bits of sticky tape wrapped around them.

 

[sutor623]

Fair enough.

 

[fincherjon@yahoo.com]

When I first got the boat I went to crank it but the battery was dead. I jumped it with a battery charger and was giving the starter a good workout! I then had to jump it again on the next attempt because the battery was dead yet again. Could this cause damage to the rectifier.

 

[sutor623]

If the battery wont take a charge or is dead it can often cause overheating of electrical charging components (stator or rectifier) because the juice has nowhere to go. So yes, running and outboard on a dead battery is not the best choice.

 

[fincherjon@yahoo.com]

The battery was charged when the meltdown occurred. I was just thinking back if something I did could have caused it. Thanks again.

 

[gm280]

Maybe the reason the battery keeps discharging and going dead is because the rectifier is toast. So that allows another path to discharge the battery via the fried rectifier. JMHO!