Help Identifying Alternator and rebuild/replace

[Neuse River Sailor]

Thanks, Tac, that is a great help and I am starting to understand. One thing that gave me problems was I saw in Don Casey's book "This Old Boat" on pages 236 and 237 a description of a field disconnect switch and it included a sketch that showed a switch in what he labeled "supply wire" which ran from the battery + to the regulator. That's why I thought I could put a switch where the isolator used to be.

But I think what you are telling me is to run the big + cable out of the alternator/regulator to the common at the selector switch and run the battery + cables to the 1 and 2 connectors. What I still wonder about, is the sketch that I posted earlier, that came from the previous owner of the boat, shows that the common already has a cable from it to the starter. So is it ok to stack the cable from the alternator on that one?

Here is my sketch of what I currently understand that I should do. I have omitted the wires that I wouldn't change from the current setup, like the one from the alternator to the coil, and the ground, which I understand isn't really a wire, just a representation of the alternator being grounded to the engine by being bolted in place. Does this look like a workable arrangement?

[Al Schober]

I had problems using the alternator foot for grounding. The problem was identified when I checked the voltage between the block and the alternator case with the alternator charging. I added a separate ground wire from the case to the block. You may not need it, but check.
Most alternators (the Motorola included) are meant for automotive use. Their regulators (internal or attached) have a control voltage that I find to be too low for effective battery charging.
The alternator itself is not a complex device. The windings that make the power are located in the case, don't rotate, and have their AC output turned into DC by diodes pressed into the case. The rotor carries the field winding, which gets its current through two brushes and slip rings.
The regulator acts to control this field current. Two types of regulators: First is P type which controls the current going TO one brush, the other brush is grounded. Second is N type which controls the current coming FROM one brush, the other brush is attached to the alternator output. The alternator has to be wired to match the regulator and vice versa.
Second suggestion is to get rid of the A/B switch and use two separate battery banks, each controlled by a simple On/Off switch. The start battery (I found no need for anything larger than a Group 24) is connected to the starter and engine loads. House bank is connected to your distribution panel, and can be configured to your liking with more/less bigger/smaller batteries.
Batteries are charged from the alternator. The system that worked best for me was to send the alternator output to the house bank. When the house bank came up to voltage, a relay (VCR) would close and send current to the engine battery.
There are lots of ways to skin a cat. I've tried several, and this is what works for me. Hope it helps.

[tac]

Neuse:

Well, Yes and/or (inclusive OR) No. I’ll be cautious. I have no idea what this “Sel Sw” is. What are it’s contacts rated for? A picture (Suitable Fo’ Framin’) of the front of this switch, and the back of the switch, is necessary. For example, as connected, it appears that a terminal (possible the Common or Output, who knows, it’s not labeled) is connected to the starter solenoid. The starter solenoid is mounted on the starter and draws only about 12A. The solenoid, when energized by the start switch, switches a large current (about 125A normally. But if the engine is frozen, or the propeller jammed, it can draw a hellacious amount more) from the battery(s) to the starter motor during the start. There is no wire size shown for this starter motor wire (supply red, return is through the engine block). It should be BIG, like #4 or #2.

As to “stacking” wire terminals, others may correct me, but I believe the ABYC and Coast Guard limit is 4 connections max on any terminal stud or screw. And that’s physically pushing it. You can get around this by using power posts (see the Blue Sea catalog pg. 102), appropriately sized for current and wire terminal size.

Ideally, the starter motor (as well as the solenoid, through the start switch) should be connected to the selector switch Common/Output along with the alternator and house loads, as roadnsky shows. This means it is Imperative that the selector switch be able to handle well over 200A. The Blue Sea selectors are designed for over 450A.

But if your selector switch is like this Hella (https://www.amazon.com/Hella-Incorpo.../dp/B000UKJN4O), and is only rated at 100A, it won’t do. So.......

Please send a picture of the front of the switch, and a picture of the back of the switch. The picture of the back hopefully will show the terminal markings.

[Neuse River Sailor]

Thanks for hanging in there with me. I'm about 240 miles from the boat, I go down there about once a month for a few days and work on it and then come home - but I did dig up a picture with the front of the switch in it:



The back of the switch I'll have to wait until next time I'm at the marina to photograph. I'm not too concerned about the switch being inadequate, the boat only has 150 amps of batteries provided for and the previous owner was a very by-the-books type who had the boat maintained by Bock Marine in NC. The issues I am having I attribute to the boat resting at the dock almost unused for about 8 years before I bought it. I think the owner enjoyed having all the bells and whistles and gradually complexified the electrical and other systems to a point that they are hard to understand for a novice. I have focused on chainplates, standing rigging, spreaders, deck leaks and so on and am just now starting to give the engine and electrical system some attention. Up here on the Albemarle there are no serious boatyards or technicians who I could turn to on these issues so I'm trying to resolve them to the extent that I can sail the boat back to the Pamlico where there are several good yards. Sorry to be so long-winded.

[tac]

That was long-winded? Ha! Compare with my last two posts.

Your photo confirms it’s a proper (and quite old - 20+ years?) battery selector/disconnect switch. It appears to be 4 position, maybe (from left to right) Both - 1 - Off - 2.

[tac]

Switch Contact Action

I should mention this afore forgetting it.

Your isolator and alternator failure may have been caused by opening (disconnecting) the alternator output while the engine was running. This causes a momentary (microseconds long) spike which results from the conversion of energy stored in the stator windings to voltage (Faraday’s Law). You will notice on the front of your disconnect/selector switch it says, “BEFORE SWITCHING TO OFF POSITION STOP ENGINE”. Well, that’s why.

But wait! There’s more!

Many “ordinary” rotary switches, and some old battery selector switches, have what are called “Break-Before-Make” contacts. That is, if the switch is in position 1 and its contacts are closed, when you turn it to position 2 the contacts first open (Break) before they reach the 2 position, where they then close (Make). As you can see, if you are in position 1 on battery #1, and the engine is running, when you switch to position 2 on battery #2, no matter how blinding-fast you are, the contacts will open, the alternator output is opened, and POP! goes another diode (or was that a rectifier?).

So most of these battery selector switches today are “Make-Before-Break”. That is, on switching from position 1 to 2, the contacts remain closed to position 1 until the switch is in position 2. Then, with the switch contacts closed in position 2, the contacts in position 1 can now open. Voila! The alternator output is never opened, and All's Well.

Well, almost all. You can still kill a running alternator by switching to the OFF position. Stop the engine first. Then switch to OFF.

[Neuse River Sailor]

This one goes Off>1>Both>2. Yes, I was severely warned when I bought the boat never to turn it to off with the engine running, but it's possible I did it inadvertently, though I doubt it. The switch itself feels a little loose as it goes from position to position, so maybe it is losing contact between settings. As you said, it's probably at least 20 years old. Anyway, my policy will be to set it to both and never change it until the engine is off, at least until I can confirm the switch is ok or replace it.

[tac]

I’ve taken your sketch of post 1 and revised it in the first diagram below to show the changes needed to remove the Isolator. I have not shown any fuses other than what is shown on the original. Some comments:

1. Your sketch shows #8 wires connecting the battery negatives. This is too small. You say in post 19 that you have 150A of batteries. Since batteries are not rated in amps, but in amp-hours (Ah), I assume you mean 150Ah. Would that be two 75Ah batteries?
2. The proper size black cable connecting their negatives might be a #0 (1/0), not a #8. Likewise, the wires going to the starter motor, to handle the 125A current, should be at least #2, not #8. The wire to the Ignition and Start switches and then to the starter solenoid, drawing a mere 12A, can be a #10 or #12, depending on the total length.
3. USCG and ABYC require fuzes within 7” of each battery. If you don’t have them, I would recommend the MRBF fuses, shown in the Blue Sea catalog on pg 64. Although somewhat pricey, they’re easy to install, and take up little room.
4. You may end up with more than 4 wires on the output terminal of the battery selector switch. If so, add a power post, like in the Blue Sea catalog on pg 102.
5. Your original sketch shows a selector switch, “SS Sel Sw”, connected by #10 wires to the “Volt Div” isolator. With the house loads now connected to the battery selector switch output, this 2 position SS Sel Sw is no longer needed. I’ve shown this on the lower diagram.

This is not meant to be a course in basic electricity. If you will be doing much of the work (and planning) yourself I recommend the following as minimum reading. It will also serve to check the work and advice of others (especially if the advice is free, like this, but also if you’re paying for it):

a) Nigel Calder’s most excellent Boatowners Mechanical and Electrical Manual

https://www.amazon.com/Boatowners-Mechanical-Electrical-Manual-4/dp/0071790330

b) USCG Boatbuider’s Handbook, Subpart I Electrical Systems

http://www.uscgboating.org/regulations/assets/builders-handbook/ELECTRICAL.pdf

c) ABYC E-11 AC and DC Electrical Systems on Boats

http://www.blackfinforums.com/sites/default/files/10/attachments/abyc-e-11.pdf

[Neuse River Sailor]

Thanks, Tac - Yes, two 75 ah batteries. That sketch with post 1 isn't really MY sketch, it's one that I found in the papers aboard the boat when I bought it. I don't think those cables are actually #8s, don't know why the sketch has them labeled like that.




The only sketch I take credit for is the rather crude one in post, I believe, 16. After long perusal I am just starting to get some small understanding of the first sketch, and I will study the ones you made for me and hopefully come to understand them. Many thanks for taking the time to make them.

This is getting too deep for me when all I want is to get from the Albemarle Sound to the Pamlico Sound, where I can find a competent mechanic. I'd sail the boat the whole way, except there are two canals enroute, one of them 20 miles long, and I'm going to have to motor through them. I need enough battery power to start the engine a few times and run it for about 8 hours.

So I'm going to wire it up like in my crude sketch, with a couple of marina friends watching me and giving me free advice. I'm going to beg, borrow or steal a small gas generator for backup. And then I'm heading for the Pamlico.

Thanks All for your advice, and thanks especially Tac for taking the time and effort to try to bring me along.

[tac]

A last post, inspired by your photo of the batteries.

1. Your proposed (simplified) hookup in post #16 looks OK.
2. The black and red cables to the batteries look like #2s.
3. The battery connections, especially the lower battery’s + lead, are badly corroded. If this is the Start battery, and you want to have a good starting engine, this connection must be seen to. Corrosion means resistance, which means voltage drop. This leads to reduced current to the starter, and slow (or no) starts.
4. For a temporary reliable, safe system, those connections need, at a minimum, cleaning up. Replacing the cables would be better. You could kill 2 birds with one stone (fuse protection, a USCG requirement, and good connection) and use the Blue Sea 5191 or 2151 terminal fuse blocks for the batteries.
5. The lower battery red cable, with the clamp-on terminal, is heavily corroded. I betcha it has corrosion underneath the jacket for some distance up the cable. If so, it needs replacement.
6. What is that tank in the lower right corner, with what looks like a Moeller 3 Way Fuel Valve? I hope it’s a water tank. If it is a fuel tank, it needs IMMEDIATE attention! The two green hoses do not look like USCG approved, ethanol rated, fuel hose (i.e. Type A1-15, SAE J1527). Besides being illegal, use of non-approved hose can, especially in the presence of ethanol fuel, lead to dissolved hose innards clogging the carburetor. Murphy’s Law dictates that this must happen in restricted waters, while dodging a 120,000 DWT tanker. The other clear, reinforced hose heading off to the left is designed for water, and has no place in a fuel system.

[Neuse River Sailor]

Thanks, Tac - that picture is of the "as-acquired" state of the batteries, taken a couple of years ago. I thoroughly cleaned the connections long ago. The three way valve is to the water tank. Since I am 240 miles from the boat, I have been scrounging through my old photographs looking for ones that generally illustrate items, but overall the condition of most things is better than now than it looks in the pictures.

Thanks again, Tac and everyone who posted or even took the time to read this thread. I'm headed to the boat in a couple of days to work on the charging system and a whole lot else and will report back on how things work out. As always, the A4 formum has come through for me, and I am very grateful.