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Old 19-03-2014, 08:09   #16
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Re: Alternator not charging issue

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all those wires are live and most likely unfused. and best to be removed. shorting againist the engine would be disastrous
That's just one example of what this idiot did. And you know what? None of these issues were noted in the survey I paid for before buying the boat.

I agree, I probably should remove the now "unused" wires, but they are part of the wiring harness that came with the engine. How "bad" would it be if I used Ancor crimp butt splices to "re-use" those wires and replace this single wire alternator with a 3 wire like the original? In other words, try to rewire the boat back to the way it was originally?

Regarding the wires to the batteries, both battery banks are connected to an "A-B-ALL" switch, and the hot lead from the alternator goes to the center post of that switch. That way I can charge either or both banks. Not the best way to do it, but I've done this in the past on other boats and not had any issues.
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Old 19-03-2014, 13:57   #17
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A sudden load drop on the alterntor from the switch changing banks can damage the diodes in an alternator. However sounds like you have had no problems with it.
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Old 19-03-2014, 14:26   #18
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Re: Alternator not charging issue

You don't need much of a connection problem to drop a volt even at 20 amps. At 20 amps .05 ohms ( which unmeasurable with most meters) will give you a 1 volt drop. Any conection that is not perfect can create that problem. Yes your wire is undersized for a 100 amp alternator. It is properly sized for a 40 amp alternator max.
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Old 19-03-2014, 14:33   #19
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Re: Alternator not charging issue

Do you have a jumper wire from the hot to the exciter terminal on the top? Some one wire regulators need this some dont. Dont expect anything like 100 amp output. Mine jumps to about 30 and settles down to 25 or so after some time of running. The good about these alternators is the cost and availability. They can be had new for around $60. Rebuild kit are around $20. The mounting didnt have to be changed for my 4.108.Wiring is simple and doesnt have to be huge. it will never see anything near 100 amps. Volts dont mean a whole lot as its dependant on battery condition and other factors. Hook an ammeter up between the battery and cable. I have one with a shunt that cost about $15. "The wires off the shunt to meter are tiny allowing meter to be in remote locale. Could you post a pic of the mounts? Maybe its missing a component.
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Old 19-03-2014, 15:15   #20
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The rated amps is basicly made by short circut resistance. The higher internal resistance of your batteries, the lower amps from alt.
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Old 19-03-2014, 15:19   #21
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Re: Alternator not charging issue

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A sudden load drop on the alterntor from the switch changing banks can damage the diodes in an alternator. However sounds like you have had no problems with it.
Yup, I'm aware of that and I am very careful not to switch the AB switch while the engine is running. I also power off the shoreside battery charger before I start the engine.
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Old 19-03-2014, 15:23   #22
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Re: Alternator not charging issue

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You don't need much of a connection problem to drop a volt even at 20 amps. At 20 amps .05 ohms ( which unmeasurable with most meters) will give you a 1 volt drop. Any conection that is not perfect can create that problem.
I wasn't aware of that. Good info to know.

The terminals are pretty badly corroded (caused by a defective shoreside battery charger over charging one of the batteries) so I will get them as shiny as I can and give it another test.

Why this guy put in a 100 amp single wire alternator is beyond me. A standard 55 amp 3 wire, like what the engine came with, is more than enough to handle the meager battery usage I put it through. If cleaning the terminals does nothing, I'm leaning towards putting everything back to original, or at least as close as I can.
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Old 19-03-2014, 18:42   #23
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Re: Alternator not charging issue

If its the alternator Im thinking of it a delco 10si. The only thing that makes it a hundred amp alternator is the way the stator is wound. You can put a non self exciting regulator in it and use the three wire connection if you want stock configuration. Theyre even cheaper than the self exciting kits. You seem to have a bad relationship with yours but if you look into it its a great alternator. That particular alternator probably had the largest production run of any alternator built. I have one powering my wind generator, one on my perkins 4.108 and enough spare parts to build another. Im not seeing why you needed custom mounts. The case is a in the compact size range of alternator cases and fit right into the perkins mounts. Thats why i thought maybe just a piece was miissing.
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Old 22-05-2014, 15:24   #24
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Re: Alternator not charging issue

Sorry to dust off an old topic, but I finally got some time to investigate this further. I first cleaned and lubed all the terminals, no change. Then I made up a jumper cable to run directly from the alternator to the battery bank. Big improvement, went from 12.5 vdc without the jumper and 13.5 with the jumper. Then I disconnected each of the jumper's leads separately to check the voltage at the batteries, the positive lead made no difference but the ground definitely did. So someplace in the mess of wiring the last owner ran, he also buggered the ground. At some point I may rip it all out and rewired the entire boat, but for now I think I'll just add a reasonable gauge (same gauge as the positive) ground wire from the ground buss to the engine ground.
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Old 22-05-2014, 16:14   #25
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Re: Alternator not charging issue

Yes, you definitely want a large gage wire going straight from the battery bank to the engine block. If for no other reason other than to provide a good heavy ground for starting, your ground has to be able to hold the amps your starter pulls or something bad will happen
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