Burned Voltage regulator

Kronos

Seaman Apprentice
Joined
Nov 20, 2017
Messages
35
Hi,

I just assembled my Merucry 2004 60HP EFI after repairing the adaptor plate and the drive shaft casing. First time I work on a boat engine so I was a bit surprised it started today - and ran for 5 or 10 minutes.... However smoke started coming from the voltage regulator - and it smells like it is toasted.

So... what could be the issue? Of course it should somehow be related to the work I have done but I cannot find any correlation. No wires seems damaged (by the disassembly/assembly), or forgotten - well there are quite a few but I looked closely.

It was cold (just about freezing), the battery was a bit low on voltage but not too much. The smoke from the voltage regulator came when I increased the RPM on the engine.

Any ideas?

One anomaly I found was a black connector in the engine harness connector - that goes to the remote control module. I measured where ever I could but did not understand where this wire goes? Someone knows? Include a picture of the female connector of the harness. I cannot find a good diagram.
 

Kronos

Seaman Apprentice
Joined
Nov 20, 2017
Messages
35
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merc850

Commander
Joined
Jul 7, 2010
Messages
2,022
Rectifier or regulator can be destroyed by battery connected backwards, battery voltage below 9v, running engine with battery not connected, boosting a dead battery to start motor, + wire from rec/reg not connected to battery etc. The alternator is not for charging a semi-dead battery just to maintain it @ 12v
 

Kronos

Seaman Apprentice
Joined
Nov 20, 2017
Messages
35
Battery was correctly connected all the time, clean connections and not under 12V before I started. Don't remember the exact voltage but low 12.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
"Remote control module"??? If you mean the remote control, ground is used there in the off positon where it is applied to the ignition modules to stop the triggers thus turning the engine off. Not a high current requirement in the module or any of the instruments that may use that ground for their performance.

If no ignition wiring was burnt, including at the connections showing signs of overheating, battery was connected properly and above 12v in this weather, I don't see an internal mechanism.

Reving the engine raises the voltage and put more load in the regulator part of the module. Only thing I can think of is that the module was not "heat sunk" properly to the mounting plate since the low battery was requiring more load than what you would expect normally, but not all that much, even though the ambient temp was low.

The operator's manual has a section covering what to expect from the regulator at different loads and rpms. Might get one with your new regulator. iboats sells both a paper copy and access to electronic ones. BTDT
 

Kronos

Seaman Apprentice
Joined
Nov 20, 2017
Messages
35
Yepp, I mean the thingy with throttle, ignition key and these things :)

Hmm, when I removed the regulatorI never noticed how it was heat sunk to the engine, or I didn't consider this at all. It is possible it was not attached properly. How is it supposed to be attached? using some paste? Or just metal to metal?
 
Last edited:

pancakes

Seaman Apprentice
Joined
Feb 18, 2008
Messages
49
out of curisoity, were you running two batteries on "all" instead of "1" or "2? i believe this can fry the rectifier/regulator if batteries are not of the same age/size.

i had a similar burned regulator/rectifier that ended much worse with the entire motor catching fire. in my case(150 efi) the on-engine fuel filter was close enough to the toasty harness that it caught and it was indeed a very scary situation. luckily i had an extinguisher on board that just BARELY did the trick. good thing too as i had my three year old boy on the boat with me. we almost had to swim from a burning boat!!!

The tach was erratic just before the event.

i believe a faulty regulator/rectifier is the #1 cause of outboard engine fires and should be changed out due to age as a regular maintenance item.

i'd love to know if anybody can confirm the "all" theory...
 

Kronos

Seaman Apprentice
Joined
Nov 20, 2017
Messages
35
out of curisoity, were you running two batteries on "all" instead of "1" or "2? i believe this can fry the rectifier/regulator if batteries are not of the same age/size.

i had a similar burned regulator/rectifier that ended much worse with the entire motor catching fire. in my case(150 efi) the on-engine fuel filter was close enough to the toasty harness that it caught and it was indeed a very scary situation. luckily i had an extinguisher on board that just BARELY did the trick. good thing too as i had my three year old boy on the boat with me. we almost had to swim from a burning boat!!!

The tach was erratic just before the event.

i believe a faulty regulator/rectifier is the #1 cause of outboard engine fires and should be changed out due to age as a regular maintenance item.

i'd love to know if anybody can confirm the "all" theory...

I have a single battery system only. However, very interesting because I actually plan to install a two battery system (with automatic charging relay) using two batteries lf different size and type. Should maybe consider using similar batteries!
 
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