Having issue achieving propper charging voltage.

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Mahoney

Chief Petty Officer
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Aug 2, 2004
Messages
537
Recently replaced my original Prestolite Alternator on my 1973 225 OMC with a one wire. The voltmeter on the boat never read more than about 11 volts, regardlessof if running or not. Previos to replacing the alternator, it was evident that the voltage on the boats meter(not perfectly acurate) would drop over the day.<br /><br />After replacing we could run all day and idle, or just sit with the fish finder, gps in cig lighter, and radio for hours and the bat always read 12 volts.<br /><br />I am under the impression that when you start and run the boat ~2000 rpm you should be reading 13-15 volts at the battery?<br /><br />What could be causing this with a new one wire alternator, but battery still reading 12 volts when checked after running all day?
 
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Trent

Captain
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Nov 17, 2001
Messages
3,333
Re: Having issue achieving propper charging voltage.

Have you checked your charging system with another volt gage.. Put a voltmeter across the battery and then start the engine. And rev the engine up to at least 1500 rpm's The voltage should go up to at least 13.5 VDC.
 
M

Mahoney

Chief Petty Officer
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Re: Having issue achieving propper charging voltage.

yes. I have a volt gage as well, and before starting it reads 12 volts, then about 11.8 or so after starting, which is odd, because after running like I stated above it seems to still retain its 12 volt charge after shutting down. The old alternator was an externally regulated alternator, and this is an internal one wire. I just taped up the lead that used to be there from the wiring harness to the external regulator.<br /><br />It didn't come with instructions for hook up, one wire, not too difficult. But did I miss something whan converting to a one wire from an externally regulated?
 
W

waterone1@aol.com

Lieutenant Junior Grade
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Oct 10, 2004
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Re: Having issue achieving propper charging voltage.

Put your volt meter on the alternator output post. You should see battery voltage there when not running. When running you should see 13.5 volts. If you do not have voltage at that post when it is not running, you have an "open" in the wiring. If you have battery voltage when not running, but it does not increase when running the new alternator is defective. If by chance you have 13.5 volts there, but less at the battery, I would look real close at any connections or crimps.
 
M

Mahoney

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Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

I will check that in a few. I did put a charger on the battery overnight and it now reads 13 volts on the boats voltmeter when not running. <br /><br />Thanks, it does seem pretty straight forward, but I am not as proficient in electrical as other things. Is it possible the battery could be causing this as well? It is a new battery as of last year, but not maintained with a full charge as it should have been when not running.
 
M

Mahoney

Chief Petty Officer
Joined
Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

I have an open in the wiring somewhere I think. INitially after taking off the charger, bat voltage read about 13.5. 3 hours after off charger, read 12.8.<br /><br />I get minimal voltage when initially connecting positive voltmeter lead to output terminal on alternator and grounding the ground from voltmeter(.30 volts) this reading slowly decreases to 0.<br /><br />Sounds like I have a connectin issie somewhere. I know it is not at the bat terminal, those are shiny new, nor the connection from the bat to the output lead on the alternator, clean and new as well.<br /><br />Any suggestions about what to look for? I know in the absence of any hints, I will be breaking out the wiring diagram and tracing everything.<br /><br />Thanks in advance. Hopefully someone has had this issue before and found a likely culprit.
 
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Trent

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Nov 17, 2001
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Re: Having issue achieving propper charging voltage.

The one wire that connects to the alternator.. Where does it go?
 
M

Mahoney

Chief Petty Officer
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Aug 2, 2004
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537
Re: Having issue achieving propper charging voltage.

thats the tough part it immediatly feeds into that 60 amp fuse, that is just an epoxy ball, then routs through to the back of the engine with a bunch of other wired I guess to the syliniod. I am not looking at the diagram at the moment, but I will check and see where it runs
 
M

Mahoney

Chief Petty Officer
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Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

looks like from my wiring diagrams, that that wire runs directly into the black cannon plug electrical connector. I guess thats a good place to start. Disconnect battery, open connection and clean out good.<br /><br />I did have aquestion on what to do with the wire that used to connect to the external regulator now that the regulator is not used and removed. Just tape up good and make sure it doesnt gorund on something?
 
M

Mahoney

Chief Petty Officer
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Messages
537
Re: Having issue achieving propper charging voltage.

OK, I can't get more than 12.8 at the battery when running. This seems a bit low. I did replace a couple wires that were badly corroded, but think the actual lead from the alt going back to the starter needs to be replaced too.
 
M

Mahoney

Chief Petty Officer
Joined
Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

OK, think I figured it out. The 60 amp fuse on the wire from my b alt terminal is blown. with ign off, 12.8 volts before the fuse, .3 volts after the fuse.<br /><br />Problem is, this fuse has this red epoxy all over it, I broke it all off, and there is an inline boltable type fuse that was there.<br /><br />Any ideas on where to get one of these or a suitable replacement?
 
L

lowshovel1

Petty Officer 2nd Class
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Dec 11, 2004
Messages
135
Re: Having issue achieving propper charging voltage.

sounds like a fusable link,any auto parts store should have them.,
 
M

Mahoney

Chief Petty Officer
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Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

thanks, Ill be checking napa in the morning. Its the kind that has a way to hook 2 wires to it with ring connectors.
 
M

Mahoney

Chief Petty Officer
Joined
Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

Unfortunately napa is closed on Sundays(not sure why they do that) But picked up a 60 amp fusable link from Schucks Auto. It is the kind contained in the plastic housing. I bolted the 2 ends from the wires to it, and used liquid electric tape liberally all over any exposed metal on the outside of the fuse container.<br /><br />I was reading more about the wire fusable links and they should never be used in this kind of application, as sever sparking can occur when they trip(I am talking about the wire type)
 
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nms1991

Cadet
Joined
May 18, 2004
Messages
25
Re: Having issue achieving propper charging voltage.

I know buzz fuses have circuit breakers that can be used in the bilge for spark aressting and you may have to look in their full catalog to find them.
 
M

Mahoney

Chief Petty Officer
Joined
Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

This fuse did the trick. Get an immediate 13.5 - 14.5 Volt charge when starting.
 
Scaaty

Scaaty

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Joined
May 31, 2004
Messages
5,180
Re: Having issue achieving propper charging voltage.

Don'tcha just love a happy ending? :)
 
M

Mahoney

Chief Petty Officer
Joined
Aug 2, 2004
Messages
537
Re: Having issue achieving propper charging voltage.

gotta love it when good ole fashoned troubleshooting does the trick.
 
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