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Charging issue.....new guy needs help!?!?!

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NewBoatDaddy

New member
Hey yall.. I'm a first time boat owner, lloonnngggg time mechanic. im completely stumped here and need some help since, it is a boat, and not all of the mechanics from auto cross over

To start
1996 regal valanti 176
3.0 mercruiser i/o
Dual batteries thru a perko switch. Pretty standard other than that

So, in my first few times taking her out, because of my ignorance to boats, I ran her on both batteries.......idiot move apparently. Now, I have no charging. I had to replace one battery and thought i needed to replace the alt. Did that twice, no change. Will not charge. If you take the battery cable off the outlet lug on the alt, you can watch the voltage slowly drop.........I've run thru and cleaned all of the grounds and gotten the total resistance down to under 2 ohms. The purple wire will fluctuate between 2 and 10.5 volts while running. The red wire will not show full battery voltage.

PLEASE HELP!!!!!!
THANKS
 
The purple wire will fluctuate between 2 and 10.5 volts while running. The red wire will not show full battery voltage.

You need to fix those issues first, the sense is constant 12V and the excite it switched 12V
 
Bt Doctur said:
The purple wire will fluctuate between 2 and 10.5 volts while running. The red wire will not show full battery voltage.

You need to fix those issues first, the sense is constant 12V and the excite it switched 12V
Click to expand...

So, if I was to jump these directly to 12v it should charge?
What are the possible fixes in this case without the work around?
 
makomark said:
Not with the engine running, I hope??? when you do this, what are you measuring - at the alternator or the wire?
Click to expand...

Sorry. Wasnt as clearly stated as I could have. You can watch the voltage drop slowly if you test at the alt output lug. Black lead on ground, red lead on alt output lug
 
for testing purposes connect both together and to the + battery. Alt should show 13.6 - 14.6. If yes, alt is good, sense and excite wiring is bad.
Work around is connect a wire from the sense directly to the + battery and the excite to the coil + side or to the electric choke feed that is hot with the ign "on"
 
Bt Doctur said:
for testing purposes connect both together and to the + battery. Alt should show 13.6 - 14.6. If yes, alt is good, sense and excite wiring is bad.
Work around is connect a wire from the sense directly to the + battery and the excite to the coil + side or to the electric choke feed that is hot with the ign "on"
Click to expand...

Yea. Hot jumped both of them. No go on the charging. Also, I'm having a consistent 11.8v on both the sense and excite wires, which I would think would be expected given the no charging and long wiring runs.

This is the second "new" alternator......not site where to go from here
 
if your doing it like this then the alt is defective, do you have 12v on the orange wire you took off the alt output post?
click to enlarge
 
.................
NewBoatDaddy said:
Dual batteries thru a perko switch. Pretty standard other than that


So, in my first few times taking her out, because of my ignorance to boats, I ran her on both batteries.......idiot move apparently.
Having your MBSS (main battery selector switch) set to ALL/BOTH will not harm an alternator.
However, it will prevent the alternator from sensing the battery voltage individually and setting the charge rate.

Switching from one bank to the other bank (engine running) is not an issue because these are what we call "make-before-break" contacts.

Unless the MBSS offers an alternator field protection circuit, passing through the OFF position (while the engine is running) may damage the alternator.


By chance did you pass through the OFF position with the engine running?
Click to expand...
 
On an 18 foot runabout, the need for two batteries is hard to justify. The purpose of the second battery is as a "house" supply for stuff like lights, electronics, pumps etc. Alternately, you need a second battery if you are using a 24 volt trolling motor. You may want to charge up the second battery before you go out and just keep it "offline" until such time that the main start battery fails. Also, it is to your benefit to have the biggest dual-purpose marine battery that will physically fit in the battery compartment.
Ugh I'm rambling.

Anyway, your main concern is the present lack of charging on either battery. The first thing to do is take the alternator to your favorite auto parts store and have it tested for output. If it passes, then you should be sure the batteries themselves are in good condition. If these both pass, then there is something wrong with the wiring. Since this is an older boat and may have been altered by others in the past, it will be a challenge to troubleshoot from a distance.
Could you post a pic of the back of the alternator so that we can see the wire colors and connections? Remember to resize your pic to 800x600 before trying to upload.
 
I've had all 3 tested here locally. 1 original and 2 "new " .. although, I dont trust the tezting because these kids here either dont know how to look up directions to run their machines or dont have the ability to do so. I'm kind of stuck with just replacing altz until it works.
 
Power straight to the red and purple post

that is confusing because the reg has wire leads with bullet connections?
If you jump the regulator as in my post and you dont read 13.6-14.8 there is no output from the alt.
Are these alt true marine alternators.
What brand alt are you trying to use?
 
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NewBoatDaddy said:
No. It was either on both or not running
Click to expand...

Good. Keep that in mind, and make sure that others on board also know about that!

NewBoatDaddy said:
I've had all 3 tested here locally. 1 original and 2 "new " .. although, I dont trust the tezting because these kids here either dont know how to look up directions to run their machines or dont have the ability to do so. I'm kind of stuck with just replacing altz until it works.
Click to expand...

Well, you'll know soon.
Make sure that the alternator's chassis Negative cable is making good continuity. This will be the small cable that runs from the alternator chassis to the cylinder block.
While some think that the alternator body and mounting makes adequate Negative contact, the small cable ensures it.
 
Bt Doctur said:
Power straight to the red and purple post

that is confusing because the reg has wire leads with bullet connections?
If you jump the regulator as in my post and you dont read 13.6-14.8 there is no output from the alt.
Are these alt true marine alternators.
What brand alt are you trying to use?
Click to expand...

They the local autozone marine brand. I've been suspect of them since the beginning. Like I said, I havent found anyone around to reliably test them. It's just odd to have gone thru 3 of them and none of them work. As far as I can see, everything else us there and they're just not working. Even if I jump the posts I still get nothing. Any recommendations on a brand that's reliable?

Bigger issue now is that it's not running. Ran for 10 minutes then died.
 
Ed makes a good point. The Delco 10si is a decent replacement. Not high end, but OK.

You can buy these in what they call a "single" wire self exciting (internally regulated).........., or in the style that requires an external regulator.

The single wire/self exciting requires a bump in RPM to become excited.
Once excited, it will remain excited until engine shut down.
This is typically not an issue.... during start up, RPM increase is generally enough to excite them.



.
 
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