Out for a short ride Saturday with a marina mate, he notices volt meters and remarks that with both showing only 12 volts there is a problem. I tell him that it's the normal reading and I don't think there is a problem. Five minutes later, wham, he jinxed it -- the starboard meter drops to under 10 v and that ain't normal. We head back to port before the battery dies.

Also needed to mention problem B: when I got onto the boat just before taking the ride, the stbd battery bank (2 batteries in parallel) was dead and I turned on the battery charger for a just few minutes before heading out. Using the solenoid xover switch, the stbd engine cranked over smartly.

Overnight Saturday, the stbd bank charged fully. Today, I put a meter on the batteries and it showed 12.6 v at rest (after that full charge) but the only same voltage with the engine running, not the expected 13.5 or so volts.

That says to me that there is an alternator problem. It's a rebuilt unit put into service only about a year ago. Tips on how to proceed are welcome. I may have rebuilt the old, original unit as a precaution so there may be a backup on the shelves.

The belt: Is it tight enough? I ask because I can turn the alternator by hand,

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Joel Albert, Potomac MD
"Charlie B" - 32' FBS
docked Deale, MD

1. Fully charged batteries should be 13.5 to 13.65 volts.

2. You need to check them with the charger OFF

3. Alternators are not designed to 'bring back' a near dead battery. It takes HOURS of running to do that, and

4. Check the water levels in your batteries. I bet you'll be stunned at what you find!

Jeff

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Only 30 days 'til splash time!

Our remote regulators are often part of the problem. I dealt with it by changing to new one wire alternators. You have to run new heavier wire from At. to you battery banks but they work much better. Slightly larger output 62 amps but still single belt. Masco was an excellent source.

dave

Joel, Belt dressing is a big no no. All that does is make a big and hard to clean up mess and if you get to much on it will cause the belt to slip even more along with some noise. The best thing to do is to clean the mess up and properly adjust the belts. New belts will stretch after a running for a while and will need to be readjusted. Check you batteries with a hydrometer and look for one or two cells with a low reading. An even better test would be a load test as this will test the internal battery connections along with the cells. A properly set up alternator will do a much better and much faster job of charging a dead battery that a 10 amp battery charger. The exception to this would be a late model automotive alternator which is not happy doing a major recharge. The ones on our boats do a good job of recharging a dead battery. One safety note -- a dead battery that is in poor condition will gas off when charged and this gas is very explosive so watch the sparks. DO NOT CONNECT OR DISCONNECT ANY THING FROM A BATTERY THE IS GASSING.

From Rick:"...A properly set up alternator will do a much better and much faster job of charging a dead battery that a 10 amp battery charger...."

-describe, pls, "properly set up alternator". thnx

From Doug: "I put the VOM across the battery but wil also check the voltmeters."

-Mine traditionally read low, only around 12 v, so your description may explain why. I always regarded that as normal, typical readout. So, when both upper and cabin meter on stbd side dropped to 10 v, I suspected a problem. New unit (rebuiilt, that is) now sitting on the boat waiting for yard's attention.

Jeff: I think I traced the wires as you described them in our conversation. But still not sure whether regulator is external

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Joel Albert, Potomac MD
"Charlie B" - 32' FBS
docked Deale, MD

Water to be added to the battery should only be distilled water. Adding municipal or well water to your battery will contaminate the acid solution with dissolved limestone, [hardness] and caustic soda used to reduce acidity from flouride additives. These alkalines react with the acid to produce salts and your battery's strength and lifespan are shortened. Cheap battery chargers left on continuously will "cook" out the water in your battery. Ideally using a three stage charger to maintain your batterys is what is needed. They start out strong at some rated at ten amps, then drop to a finish charge of two amps. When the battery is fully charged, they then perodically send a .02 amp charge through to keep the battery topped off. There is a system where the charger will choose which battery bank needs a charge and then alternates back to the weakest bank.

Jeff: Great photo w/captions. I will have to get unlazy and remove the metal plate that covers the electrical components, the one with the big (2")rubber plug in it and check what's underneath. It's a PITA job.
Jim: I agree with your post and use distilled water. Also, I don't leave charger on even though it's supposed to do all you describe (Charles brand charger, about 12 yrs old) except, perhaps, select between the two battery banks.
Rick: Order #1 for the yard is to tighten belts on both sides since there is obvious slippage. Wires all appear tight & clean. Glad you posted that for everyone's benefit.

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Joel Albert, Potomac MD
"Charlie B" - 32' FBS
docked Deale, MD

I have seen a number of alternator problems that were caused by poor connection between the alternator and the block. Automotive wiring harnesses often lack a ground wire just for the alternator.

A good cure is to run a heavy (8 awg) wire from the ground stud on the alternator case to the same bolt to which the battery ground strap is attached. The recommended attachment for the battery negative is to one of the bolts that secure the starter motor to the block. That way the battery gets hooked directly to the case of the starter.

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"I remember when welfare was for poor people..."

You have a mechanical fuel pump--see doctored photo.

Jeff

Fastjeff attached the following image(s):

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Only 30 days 'til splash time!

The output for the alternator is usually easy to spot - it is an insulated stud, often with a plastic guard, and the wire attached to it should be heavy and either red or orange. Red is common on automobile engines.

There is usually another connection, small wire, that goes to the (purple) ignition. This powers the regulator. If you have an external regulator (rare these days) then it is a field connection and will go to the regulator.

The negative is internally connected to the alternator case, so the whole shebang is negative. Usually there is a stud mounted to the case directly to permit attaching a wire. When you put an eye terminal on the stud (using an aircraft nut, please), the connection is normally made directly to the case. On some (older) cars, the designers assumed that the connection to the block would be through the brackets. This is a bad idea around water. New harnesses have a black wire that is supposed to go to the case. Better to go directly from the alternator case to the block yourself.

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"I remember when welfare was for poor people..."