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Alternator overcharging?

Your old Chris-Craft electrical system can be a challenge. If it runs on "juice" pose your questions and offer your advice here.
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JimF
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Alternator overcharging?

Post by JimF » Mon Sep 30, 2013 8:46 am

I have finished the installation of 2 327's in my Sportsman and have run them for about 2 hours on the lake. I am wondering if the port engine is overcharging as the dash voltmeter seems pretty pegged to the 18 end of the scale. The starboard was at almost 18 but now has dropped back to more normal position. Both alternators and batteries are new. Could the port battery just not have been very charged when I bought it and is still trying to become fully charged?
1930 Chris-Craft Model 100 20' "MOXIE"
1940 Chris-Craft Red and White 25' "Old Paint"
1946 Chris-Craft Sportsman 25' "CinCity"

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Re: Alternator overcharging?

Post by farupp » Tue Oct 01, 2013 8:46 am

Jim, assuming you boat has a standard 12 volt system with 12 volt batteries, the alternators should be charging the batteries at no more than about 14.5 volts, and when the batteries are fully charged the alternator output voltage should drop to about 13.6 to 13.8 volts. Charging at 18 volts will destroy the batteries. Fully charged, new batteries should read about 12.5 volts at rest without the engines running and no current draw on the batteries.

For clarification, do you have volt meters on the dash or amp meters? If they are amp meters and not volt meters, a reading of 18 amps while charging a battery is acceptable until the batteries are fully charged. At that point the amperage reading should drop to about 3 to 5.

There was an excellent article on page 46 of the Summer 2007 Brass Bell about batteries and their charging. I'm not sure why your alternators are putting out 18 volts (or more) unless the regulators (which may be internal or external) are defective.

Frank
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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Re: Alternator overcharging?

Post by jfrprops » Wed Oct 02, 2013 8:25 am

Whoa! something is very wrong with that scenario....get it figured out before running her much more....lots of good info on here....previous post is right on.

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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JimF
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Re: Alternator overcharging?

Post by JimF » Wed Oct 02, 2013 8:34 am

I am taking the alternator to the dealer this morning to have it checked out. It is a single wire unit so I assume it has a built in regulator. That wire goes straight to the positive on the battery.
1930 Chris-Craft Model 100 20' "MOXIE"
1940 Chris-Craft Red and White 25' "Old Paint"
1946 Chris-Craft Sportsman 25' "CinCity"

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Re: Alternator overcharging?

Post by jfrprops » Wed Oct 02, 2013 9:30 am

you must still be running a ampmeter....????
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

farupp
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Re: Alternator overcharging?

Post by farupp » Wed Oct 02, 2013 9:37 am

I think he does have ampmeters and not voltmeters on his 1959 Sportsman dash. That's what the boat came with originally, and why I wanted him to be sure what meters he had before running the boat any longer.
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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JimF
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Re: Alternator overcharging?

Post by JimF » Wed Oct 02, 2013 9:41 am

get-attachment-79.aspx.jpg
No these are voltmeters. When I had the instruments restored I went to all electric instruments, tach, temp, oil and volts.
1930 Chris-Craft Model 100 20' "MOXIE"
1940 Chris-Craft Red and White 25' "Old Paint"
1946 Chris-Craft Sportsman 25' "CinCity"

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Re: Alternator overcharging?

Post by farupp » Wed Oct 02, 2013 9:53 am

Thanks for the clarification, Jim. Do the voltmeters go in the open holes on the dash plate?
If the voltmeters are reading 18 volts output from each alternator you do have a problem.
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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Re: Alternator overcharging?

Post by farupp » Wed Oct 02, 2013 10:31 am

How many volts does each voltmeter indicate with the ignition on and the engine not running. Each meter should read about 12+ volts which indicates the voltage from each battery without the alternator charging the battery.
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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Re: Alternator overcharging?

Post by JimF » Wed Oct 02, 2013 10:48 am

Both engines read about 12 volts with the keys on but engines not running. I just had the port alternator,the one that reads 18, tested and it is fine. I think my next step will be to test the voltage at the battery when the engine is running. I will not have the boat available until next week. Faulty gauge?
1930 Chris-Craft Model 100 20' "MOXIE"
1940 Chris-Craft Red and White 25' "Old Paint"
1946 Chris-Craft Sportsman 25' "CinCity"

farupp
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Re: Alternator overcharging?

Post by farupp » Wed Oct 02, 2013 10:56 am

It could be a faulty gauge but do both gauges read 18 volts when the engines are running or just one? If one read about 13.5 volts and the other reads 18, the gauge indicating 18 could be bad. If it is easy to do, switch the wiring on the gauges so that they are reading the other battery. As you said, you also could check the voltage output from the alternator at the battery and see what it reads. If it is about 13.5 or a little more and the volt gauge reads 18, it would indicate the gauge is wrong.

It sounds like you are getting to the cause of the problem.
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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Re: Alternator overcharging?

Post by JimF » Wed Oct 02, 2013 12:08 pm

Yes, currently (pun intended), one reads about 14 and the port reads 18. I think I can easily switch the gauge wires although that sounds scary. The engines are grounded together but it makes sense that switching them they would still go to the same ground. I will give it a try when I get the boat back from the cover shop the first of next week. Thanks for all your help.
1930 Chris-Craft Model 100 20' "MOXIE"
1940 Chris-Craft Red and White 25' "Old Paint"
1946 Chris-Craft Sportsman 25' "CinCity"

farupp
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Re: Alternator overcharging?

Post by farupp » Wed Oct 02, 2013 12:53 pm

All the grounds (-) on the boat eventually end up at the same location on the engine block and/or the negative terminals of the batteries. Be careful of the positive side (+) of the connections to the volt meters. Disconnect the batteries before you switch them.
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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JimF
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Re: Alternator overcharging?

Post by JimF » Sat Oct 05, 2013 2:12 pm

get-attachment.aspx.jpeg
I think this might be a combination of gauges not quite calibrated and operator ignorance as to how to read this type of gauge.

I ran several tests today. Both batteries when just sitting there with nothing turned on read 12.6 volts on my volt tester.

Turning the keys on, but not starting the engines, port appears to read 16 and starboard 13.

With the engines running, testing across the battery is 14.6 on both batteries. Testing at the back terminals of the gauges is 14.6 for both.

The picture is the starboard gauge with the engine running about 1500 RPM. Testing across the back is 14.6. I forgot to take a picture of the port gauge when it was running but the needle on that one is just slightly higher than this but still on the white dot. I was thinking that the white dot was full 18 but maybe the needle can go even higher and actually reach the 18. If the needle can go to 18, then where it is sitting is about halfway between 12 and 18, or about 14 and I am worrying about nothing?
1930 Chris-Craft Model 100 20' "MOXIE"
1940 Chris-Craft Red and White 25' "Old Paint"
1946 Chris-Craft Sportsman 25' "CinCity"

farupp
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Re: Alternator overcharging?

Post by farupp » Sat Oct 05, 2013 4:42 pm

The batteries at 12.6 volts without the engine running is just right for a fully charged new battery. The alternators should be charging the batteries at about 13.8 volts.

Then the mystery: the gauge markings. There is a big dot over 12. That makes sense. I don't know if the big dot near the 8 indicates 8 volts or ? Same with the bid dot near the 18. But, what readings do the little dots indicate? 10 volts and 14 volts? I don't know.

It is also strange that when you turn on the keys and the engines are not running the voltage readings jump to 16 and 13 volts from 12.6. Why, as that should not be the case?

Regardless, if the alternators are putting out 14.6 volts to new fully charged batteries I feel that is too high. The output should be no more than 14 volts. Therefore I would have the output of the alternators checked again. Maybe someone with more knowledge of alternators can offer more information on the correct output.

Also, I think the gauges are not accurate. Therefore, I would trust your volt meter readings and not the gauge readings. You may want to verify your volt meter readings with another voltmeter.
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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Re: Alternator overcharging?

Post by jfrprops » Sat Oct 05, 2013 6:46 pm

I don't think you have a problem...just old not very well calibrated gauges.

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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JimF
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Re: Alternator overcharging?

Post by JimF » Sun Oct 06, 2013 9:36 am

Actually I just paid quite a bit of money to have those volt gauges, and all the others, restored. The funny thing about a twin engine boat, everything costs twice as much!

I think I am OK here. As long as the volt gauge indicates more than 12, I am charging, even if I don't know how much. I think that my reading of 14.6 might drop to 14 after running the boat a little longer. These tests were done in the driveway and the alternators may be trying to recharge the batteries after they had to crank the engines a little to get them started.
1930 Chris-Craft Model 100 20' "MOXIE"
1940 Chris-Craft Red and White 25' "Old Paint"
1946 Chris-Craft Sportsman 25' "CinCity"

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