Electrical Problem

[caswensk]

First off, I know electrical problems are difficult to pin down on the internet. They're hard enough when you're there, much less trying to interpret what another person writes.... but bare with me.
My 1977 Marlin basically has the 455 Packajet set-up. Motorola Alternator and American Yazaki dash cluster. Each of the two batteries reads 12.6 volts. The alternator is producing about 13.8 volts when running. The boat is not charging. I have replaced nearly every wire in the thing and can't track down the problem. I can read 13.8 volts at the starter, at the alternator, and at the terminal board. The battery still reads 12.6... I have not replaced the ballaster resistor. What is this and could it be the problem? Anywhere else I might be overlooking? I'd say ground, but I can't find a problem..... :confused:

[Oldsquirt]

It is not the ballast resistor. That is an ignition component.
I assume when you say you have 13.8 at the starter, you mean on the Battery cable terminal. This would indicate that the output is getting at least that far. On a single battery setup the battery cable would complete the path to the battery.
What sort of device are you using to switch the batteries?

[caswensk]

It's a dial switch from West Marine. Select off, bat1, bat2, or both. I will try to disconnect the switch entirely and just direct route one battery to see what I get....

[caswensk]

Don't know what to say. I removed the switch and directly connected the battery to the starter leads. I can read 13.4 to 13.8 at the starter when running, however, the battery will not read higher than the 12.6 volts it reads running or not....

[Oldsquirt]

If you ran a cable directly from the battery to the terminal on the starter, and still show low voltage at battery, take a close look at your ground cable(s). Make sure they are not connected to a painted surface on the engine block.
Just as a test, with engine running, connect negative lead of voltmeter to a battery negative and the positive to a GOOD ground on engine. Have meter on a low(2 volt?) scale. Tell me what it reads.
While you are at it, perform a similar test on the positive side. Connect voltmeter to Bat + terminal and battery cable terminal on starter.
These tests are called "voltage drop" tests. The "goal" in this type of test is a low-to-zero reading.

[909]

does the boat continue to run with the batts disconnected? The voltage is low for the batts if they are fully charged at testing. They should read 13-14 volts fully charged. Sounds to me like it's a battery problem, not a charging problem.

[Rexone]

Sounds to me like a battery problem, or a cable problem, or a ground problem, all as others mentioned above. Take Oldsquirts suggestion and do the voltage drop tests to track it down to the point where the voltage goes away. These types of problems can be isolated pretty quickly that way.
Also it would be unlikely that "both" your batteries were bad identically. Due to that I suspect cables or grounds or corroded cable connections right at the batteries. Again the drop tests should isolate the problem point.

[roostwear]

Why do you say the batteries aren't charging? Wiill it not crank over, or are you just going off the readings? A battery WON'T show much more than 12.6 volts.... if it does, it's OVERcharging. Typically, an older alternator will put out between 13.5 and 14.5 volts to maintain 12 volts (nominal) at the battery.

[caswensk]

Yes, I realize that a battery won't hold a charge much over 12 volts, but when the engine is running (and the alternator functioning) one should be able to read about 13.5 to 14.5 volts at the battery. This does not mean the battery is charged beyond 12 volts, simply that a higher voltage is being delivered to the battery. When i start my boat, I can read only 12.6 volts at the battery... after they've been fully charged for a few hours. When I use my boat for any length of time, the charge goes down significantly. I have been forced to use battery number one to run the boat, and then if I shut it off for any reason, switch to number 2 to star it back up, because number one has dropped to about half charge... not enough to crank the engine.

[SmokinLowriderSS]

I'm smelling either a battery problem or a cable problem.