Where the heck is my voltage? Update--FIXED

[tuned]

Crud.
Here's the story. Coming home last night (in the dark), engine coughs once or twice and then just dies. I waited a few seconds and started it up and checked gauges-all OK except for voltage is low like I'm not charging. It dies again, so I drop anchor before I blow to shore.
After waiting a few minutes and checking my Alt Belt, which was OK, I started it again and it seems to be running better except voltage is still low. I pull anchor and limp several miles home at low RPMs, keeping an eye on temps and oil pressure etc...
Once I got tied to dock, I started it and revved it up. Seemed to run just fine, although still low voltage.
Didn't get a chance to go out there today, but I guess the next step is to wiggle all the connectors I can find in the area. From the abruptness of the shutdown, I'm suspicious of the regulator having a catastrophic failure and somehow 'spiking' the system.

Since it is pretty hard to get at the wiring in that area in order to follow test procedures, I'm tempted to just pull alternator and regulator. Not even sure if regulator is mounted on the alternator as Merc seems to have several kinds of each.
What's even more sucky is that the only guy I know of that had a bench set up to test and rebuild this kind of stuff just retired. Small towns suck for these type of problems. Might be easiest to just replace both and see what I get.

Other option is to take the whole boat to the Merc dealer that I am not too impressed with. Crud.

[slingshot]

It would help I you'd tell us what boat and motor you have but I'm assuming you have a Merc I/O 4 or 6 cylinder. Either way your in luck because both engines are very easy to diagnose charging issues. As a general rule no charge issues are going to be caused by one of 4 things. Bad wiring, bad alternator, bad regulator or bad battery. Do cheap stuff first. You are on the right track by cleaning all battery and wire connections. Next, take a electrical gauge and see what kind of volts you are getting at the battery in order to rule out a dash gauge issue. With engine off and voltage gauge attached directly to the battery you should be getting about 12 or more volts. short of a load test, this indicates that your battery is good. Next, start your engine and check for volts, If your not going above the volts you had with the engine off then your alternator is more than likely bad. If volts go above 14.2 or so then you have a bad voltage regulator. You can pull the alternator and take it to advance auto stores or some other stores out there that have an alternator tester. They test for free. Just hook it up and check for volts. This video shows the process on a car but it's basically the same thing on your marine engine. Good luck.

http://www.youtube.com/watch?v=ofhrTfBR0g8

[tuned]

Thanks for the reply, Slingshot.
Motor is a Merc 454 I/O. Most of those steps have been done already.

The voltage tests were done the night of the failure. I had readings from two different gauges (analog and digital) from two different wires feeding forward. 12.4VDC at rest. 12.4VDC while running. A dash gauge issue wouldn't have killed my motor.

Battery is known good. It even still started it. Battery issue wouldn't cause an instant failure/shutdown.

I wiggled and tightened all the wires.

Regulator (which I suspect) can either produce high voltage OR low voltage, not just high as you stated. I watched the vid. I agree in that it is more likely the regulator if too high of voltage is produced, but they act as sort of a switch and can refuse to send anything through, thus the low voltage. In fact, some of the old ones were actually some sort of relay.

Alternator is certainly a possibility as well, although I am not sure they would fail that quickly, unless the rectifier went out. I don't think there is anyone in town that can check it. I didn't have the right tools when I went out there, so I couldn't pull it yet.
Crud.

[slingshot]

OK, the shade tree mechanic thing to do would be to change them out one at a time. Go cheapest part first which would most likely be the regulator. Return it if that's not the problem and try a new altenator. Maybe a little expensive that way but probably cheaper than a marine mechanic. Solved a lot of problems real inexpensively that way in the past for me. Returning the part might be mildly unethical

[BoatCop]

You alternator probably has an internal regulator.

Put a meter on the alternator poles, or if it's a single pole type, one lead on the output pole and the other on ground. (any metal on the engine will do). Rev the engine to see if the voltage goes up. If not, then pull the alternator and take it to a shop and have it tested. They can tell if it's the alternator itself or the regulator. Auto Zone (or whatever it's called in your region) will check it for free.

If it's bad, don't be just buy a Chevy replacement alternator. While you might be tempted to when you look at the difference in price between an Auto Zone or Pep Boys rebuilt unit ($) and a Marine unit ($$$$), DON'T!

Marine Alternators (and starters and distributors, not to mention fuel pumps) are designed to shield any inherent sparks and prevent ignition of any fuel vapors that may be in the engine compartment.

Just about every boat fire I've investigated, and I've investigated dozens over the years, have been caused by automotive components.

[tuned]

Thanks Alan. I NEVER use non-marine components for that reason. I'm so anal about it that I always buy marine rated wiring, breakers etc...
I don't think there is a local place that can test.
I pulled the whole thing out tonight. Regulator is mounted on it. I'm just gonna replace the whole mess as I am not even sure how old it is. No numbers showing. It might be original equipment which puts it at twenty+ years old.
I also wiggled and tightened every large wire in the system.
I couldn't get at the alternator wiring posts to do any live testing, so I just pulled it.

[bradm]

Todd,

Do you have multiple batteries with a battery selector switch? I seem to recall when I installed the dual battery switch on a prior boat that you could fry the alternator or voltage regulator if the battery switch was turned through the off position with the motor running. Been a few years, so don't recall specifics, but just a random thought.

[tuned]

Todd,

Do you have multiple batteries with a battery selector switch? I seem to recall when I installed the dual battery switch on a prior boat that you could fry the alternator or voltage regulator if the battery switch was turned through the off position with the motor running. Been a few years, so don't recall specifics, but just a random thought.

I have 2 batteries with an automatic 'combiner' with no multi-battery switch at all. I guess it is a remote possibility that the combiner relay clicked ON and did something. I doubt it tho, as these relays have been around for years without problems. I am on about my 5th one in various boats and have never had an issue.

Update: I just popped for a complete new setup including regulator. $70 from eBay delivered. So a few days in dry dock and I should be back in the game

[tuned]

Cha CHING!
One dropped wrench, one bloody knuckle.
Al is back, with shiney new high-output alternator charging like a champ.

"All's well as ends better"--The old Gaffer

[Bryden24shp]

Now, go run that beast and have fun! Glad she is fixed...