High system voltage burned out regulator

[Flubadub]

Orignally, my 1988 Merc 100 had a 10 amp alternator and rectifier. Once at a remote location I had to pull start the motor thinking the battery was discharged. It was actually an open cell and before I realized what was going on, the resultant high voltage burned out several gauges and the fuel tank sending unit. In 1989 I replaced the rectifier with a rectifier/regulator and terminal block for the tachometer connection. It has worked perfectly never exceeding 14.5 volts. Last week I tested the motor in the driveway and the battery seemed weak when I tried to start. Dealer tested the battery and I decided to replace the battery rather than risk spoiling a vacation. I now have a group 24 marine starting battery that seems to have plenty of juice, but all last week the voltmeter would climb up around 16 volts. Operating the power trim would lower the voltage for a bit and where it used to climb up to 14.5 volts it now would go to 16+. I ran with the lights on to keep the volts down since the magneto tops out at 10 amps anyway. Well, the last day I went to test the electrical system (by the book)testing the output voltage and by placing an ampmeter in series with the regulator output. There was a hint of the beginning of something going on in the regulator (discoloration on the encapsulant on the regulator). I wasn't sure what I was seeing, so I put it all back and everything seemed fine until this hideous black smoke and tar started shooting up out of the regualator. So, here is the question: Is there anything that a otherwise normal Group 24 marine starting battery can do to, what I would guess, act like it has an open cell and not take the charging system output? By the way, I put the battery on an external charger to simulate a 2 or 10 amp non-reguated outboard and the volts climbed as on the boat. I tested the external charger on two other batteries and the charger voltage topped out at 14.x+. Now I am looking at $160 for a new regulator unless I can prove the battery was the source of my problem. What's up?

 

[sprinkler]

Re: High system voltage burned out regulator

Where did you buy the regulator from? What is the amperage on the output of the regulator? A linear regulator is a very simple device -- it simply chews up the power inside in order to regulate the output. So if the input of the regulator is about 16V (the voltage on my 1988 100hp), the output is 14.5V, and the regulator is putting out 2A, the wattage dissipated in the regulator = 2*(16-14.5)=3W. So what I'm wondering is if your regulator is designed to handle the power it was dissipating. When you mention discoloration on the regulator this is what I'm thinking may be the cause.

 

[Motor Boater Bill]

Re: High system voltage burned out regulator

Check all your electrical connections for corrosion. If they are not clean and tight, this can cause voltage issues, heat, and all kinds of problems.

 

[Flubadub]

Re: High system voltage burned out regulator

The rectifier/regulator setup that has been in use since 1989 is the Mercury unit that will handle the higher 24 amp output from the optional and later model outboards. The original 1988 100HP Merc had a 10 amp stator output to a rectifier and then connected to the main battery lead on the motor. The 1989 setup replaced the rectifier with a terminal block where the grey tachometer lead connects (replaced Faria tach with Teleflex) and the new rectifier/regulator sits atop the airbox adjacent to the oil tank cap. And, yes everything is clean and tight as the boat has been garaged since new and maintained. Sprinkler mentioned that the regulator has to dissapate excess output where an alternator output is regulated by a variable field. So, now the question is; did the regulator go bad coincidentaly and in the future on real hot summer days, should I turn on the lights to dissapate the output there rather than build up the heat in the regulator? That bad boy does get HOT and I guess the heat sink could be bigger or even water-cooled.

 

[Scali]

Re: High system voltage burned out regulator

I think you have the wrong battery, I have no voltage regulator 1994 40 merc & it puts out as high as 17.5 volts, from a ton of research I did on this if you have the correct marine battery & put a load on the system { I keep my running lights on most of the day } it will bring the voltage down & do no harm.<br />Granted I have basiclly no electronics but a 12 V port for my handheld & spot , lights & horn but have been running it this way for the 60 hours I've owned the boat with no issues except having to add distilled water every couple months.<br />But I believe you need a deep cycle battery for that motor with it's voltage issue..

 

[sprinkler]

Re: High system voltage burned out regulator

So what was the amperage on the regulator output? It isn't clear in your original post.

 

[Flubadub]

Re: High system voltage burned out regulator

It was putting out about 9 amps. The battery that came out was a 24DC, I think that was a deep cycle. The batteries before that were; hybrid starting/deep cycle, starting and the original battery that came with the boat was a Stowaway DC the sealed kind almost like a gel-cell. That was a big mistake as I understand that kind of battery is murdered by charging systems with no regulator. So, other than the first battery that went open, all the other types of batteries never caused the charging system to exceed 14.5 volts or so. Someone suggested a CDI/Rapair regulator that would be half the cost of a Merc. Anyone familiar with that unit?

 

[ronmold]

Re: High system voltage burned out regulator

Here's how older merc charging systems worked: The stator, generally a 4 to 9 amp unit, puts out an AC voltage on it's 2 yellow wires that vary in voltage (and frequency this is where the tach lead comes from) according to the motor RPM. This AC is converted to DC by way of the rectifier which is 4 diodes in a "bridge" configuration. This voltage also varied as to the RPM. Merc's original design used the fact that the battery acted as a load, always taking a few amps even when charged. This few amp draw shorted the output of the low-amp stator enough to cause almost "self-regulation" of the charging system output, hence many of the older motors had no regulator. With battery technology improving (less full-charged draw) and the need for more amps because of all the new marine electronics available, the motors started coming with higher output stators and the battery couldn't self-regulate anymore. Merc started putting on a regulator that would sense the DC voltage from the rectifier and short one of the yellow stator leads to ground when the voltage got too high. This along with the battery draw would keep voltage constant. Problem with this is if a battery post loosens and doesn't take some of the extra amps, or you put on a CDI high-output stator,(like I did) that sorry regulator has to do overtime work and fries! CDI makes a great unit that rectifies and regulates, not by shorting out the yellow leads but by increasing the resistance of the charge circuit when the battery voltage is at 14 where it should be. This keeps the stator much cooler also.<br />This is not a direct factory replacement but if you can find a mounting place for it, bolting it to some engine block metal for a heatsink, it sure works great on my old 175, cheaper than merc parts also. Pull the old rec./reg, toss them in trash, hook the 2 yellow wires to stator & the black & red to ground & 12v+, perfect 14V!<br />CDI #194-5279 I got mine from:<br /> http://www.seilermarine.com/rapair/mercury.htm

 

[JCH55]

Re: High system voltage burned out regulator

Dasboot, I saw your reply and have a similar problem.<br />In 2003 , I replaced my stator with a CDI 174-9710k1 from Seiler Marine on my 40 HP Mariner 4 cylinder. It has run fine with the exception that I have had constant battery problems. I have replaced 2 or 3 batteries under warranty, it is though there has been a constant load on the battery when the motor is off.<br /><br />Recently, my voltage regulator fried. Burnt wires and cover plate. From your recent reply, you mentioned something about changing to the high voltage of the new stator and that it requires changing the voltage regulator. <br />Questions:<br />Did the new stator cause the voltage regulator to fry?? <br />Has this been a common problem for the CDI stator??<br />If so, it seems to me that CDI should provide a new voltage regulator to resolve this problem.

 

[Laotzu]

Re: High system voltage burned out regulator

I installed a CDI regulator/rectifier in my '91 50hp several years ago. The prior owner had updated to a red stator. I ended up with the same problem you did, a burnt regulator. Probably for the reasons stated by Dasboot. On mine it fit in where the old rectifier was, backed against the block for heatsink. Works fine so far. <br /><br />Jerry

 

[Laotzu]

Re: High system voltage burned out regulator

JCH55, did you upgrade to a red stator? If so, that's how my regulator burnt. When I called Mercury, they said with a red stator you need to install a Merc regulator/rectifier but I bought a CDI one which works fine so far.<br /><br />Jerry

 

[JCH55]

Re: High system voltage burned out regulator

Laotzu, I upgraded to a black 16 amp stator from CDI. I believe it was the 174-9710k1. The original was the 16 amp OEM from Mariner.<br /><br />I think I would be better off going with the CDI regulator, seeing as I have their stator. You would think their components would be compatible.<br />Do you agree??<br />Thanks,<br />JCH

 

[Laotzu]

Re: High system voltage burned out regulator

Don't know who made my stator, but I assume Merc. Others on this forum think CDI is better made, and also cheaper. I don't think it makes a difference to mix and match. CDI references the OEM part number besides their own # and we can assume the part is made to duplicate Merc. spec.<br /><br />Jerry

 

[ronmold]

Re: High system voltage burned out regulator

JC, Have you checked battery voltage at higher RPM's? I replaced the stator on my 175 with a CDI 16 amp version which was all Twin City Outboards had in stock and I needed to get out on the water that weekend. If I would have ordered a CDI 9 amp unit I might have been OK, or not, the motor was getting fairly old (86) and all the other electronics have failed/worn out so I'm glad I upgraded

 

[Flubadub]

Re: High system voltage burned out regulator

It looks like the Merc voltage regulator 815279 is not available ($158.65) and the only option I see is the CDI complete with the mounting kit for about $108. At this point I see no option but to get a new reg and keep a real close eye on the electical system. I know it sounds like some kind of Voo-Doo evil magic, but I still think the new battery has some kind of wierdness going on inside. You will be the first to know when I find out.

 

[sprinkler]

Re: High system voltage burned out regulator

Did you pop the caps and see if the plates are exposed? You may need to add distilled water.