Replaced alternator, battery still not charging

[natureschild88]

I'm running a '91 Mercruiser 4.3L V6 hooked up to an Alpha 1. The battery died in the boat about a month ago and I replaced it with a new marine battery from Walmart. The new battery lasted 2 outings before it died also. I ordered a replacement alternator thinking this would fix the problem. The new alternator is marine rated with 65 amps and bolted right up to my engine with ease. The old alternator on the boat looks like original equipment from 1991, and after removing it I noticed there was a good amount of rust on the back of it and near the connections for the wires. I cleaned the rust off the connections and installed the new alternator, double checked to make sure I had all of the wires ran to the proper connections. I thought that with the rust on the old alternator that replacing it with this new one would definitely do the trick.

I recharged both the new and old batteries and brought both out on the boat just in case something failed again. The new battery ran fine and started the boat 4 times until it failed once again. I hooked up the old battery and was able to start the boat with it and head back in.

I just took the old alternator in to my local auto parts store to have it tested. I was thinking maybe even though it looked old and crappy, maybe it isn't actually my problem after all?? The auto parts store said they could not test boat alternators because the wiring is different from car alternators. A random guy in the store overheard my story and mentioned checking my "inline fuse something or other" and that it may be the problem, not the alternator after all.

I'm supposed to take the boat out for a week vacation in 2 days, any help would be greatly appreciated!!

And also, my boat has a voltmeter. When the battery is charged and the boat starts it reads about 12 volts. When the batteries don't have enough juice to spin the motor over it reads closer to 11 volts. All wire connections look clean from any corrosion. Please help!!

 

[natureschild88]

Replaced alternator, battery still not charging

I'm running a '91 Mercruiser 4.3L V6 hooked up to an Alpha 1. The battery died in the boat about a month ago and I replaced it with a new marine battery from Walmart. The new battery lasted 2 outings before it died also. I ordered a replacement alternator thinking this would fix the problem. The new alternator is marine rated with 65 amps and bolted right up to my engine with ease. The old alternator on the boat looks like original equipment from 1991, and after removing it I noticed there was a good amount of rust on the back of it and near the connections for the wires. I cleaned the rust off the connections and installed the new alternator, double checked to make sure I had all of the wires ran to the proper connections. I thought that with the rust on the old alternator that replacing it with this new one would definitely do the trick.

I recharged both the new and old batteries and brought both out on the boat just in case something failed again. The new battery ran fine and started the boat 4 times until it failed once again. I hooked up the old battery and was able to start the boat with it and head back in.

I just took the old alternator in to my local auto parts store to have it tested. I was thinking maybe even though it looked old and crappy, maybe it isn't actually my problem after all?? The auto parts store said they could not test boat alternators because the wiring is different from car alternators. A random guy in the store overheard my story and mentioned checking my "inline fuse something or other" and that it may be the problem, not the alternator after all.

I'm supposed to take the boat out for a week vacation in 2 days, any help would be greatly appreciated!!

And also, my boat has a voltmeter. When the battery is charged and the boat starts it reads about 12 volts. When the batteries don't have enough juice to spin the motor over it reads closer to 11 volts. All wire connections look clean from any corrosion. Please help!!

 

[hivoltg]

Re: Replaced alternator, battery still not charging

My guess is you got something sucking juice from the battery or a short. If you have a multimeter I would first check voltage with the motor on and off to verify you see a rise in voltage with the alternator spinning. Just a quick easy alternator test.

Next I would check for current (amps) on the ground side with nothing turned on. The multimeter inbetween the - on the battery and the main ground cable. If you have an amp reading something is sucking juice.

 

[stonyloam]

Re: Replaced alternator, battery still not charging

Get yourself a little digital voltmeter and measure the voltage on the battery: A fully charged battery should read about 12.6 Volts. With the boat running at about 1500 rpm read the battery voltage, a properly operating alternator will be putting out a little over 14 volts. That will tell you about your battery and alternator. One other thing to try is measure the voltage on the battery when the boat is cranking. If it drops below 10 volts or so it may indicate a battery problem. Charge up your batteries and take them to Walmart where they can do a load test on them. Good luck.

 

[natureschild88]

Re: Replaced alternator, battery still not charging

Just did the test. With the boat idling at 800 rpm, I'm reading 11.6 to 11.7 volts. When I rev motor at 2000 rpm this does not change. When I turn off motor I get 11.7 to 11.8 volts. When i turned the key and the starter spins the motor I dropped down to 7 volts for a brief second, and as soon as the motor started went back to 11.6 to 11.7 volts.

Is there any part somewhere along the way between the alternator and battery that may be bad?

 

[natureschild88]

Re: Replaced alternator, battery still not charging

Any ideas?

 

[Bt Doctur]

Re: Replaced alternator, battery still not charging

Yes, a couple. measure the battery and record reading, start engine to 1500 rpm, read battery and post reading.

Go to the orange lead on the alt, take a reading and record.should be reading the battery voltage. If there is no reading alt is not connected to the battery cable at the starter. If there is battery voltage, start engine to 1500 rpm and record reading. Should be higher than battery voltage or the Alt is bad or not hooked up properly.
did you do any work around the starter?

 

[natureschild88]

Re: Replaced alternator, battery still not charging

Yes, a couple. measure the battery and record reading, start engine to 1500 rpm, read battery and post reading.

Go to the orange lead on the alt, take a reading and record.should be reading the battery voltage. If there is no reading alt is not connected to the battery cable at the starter. If there is battery voltage, start engine to 1500 rpm and record reading. Should be higher than battery voltage or the Alt is bad or not hooked up properly.
did you do any work around the starter?

I had not looked at the starter on the boat whatsoever until now... Wow... What an excellent call on the orange wire.

I looked back by the starter and saw an orange wire right away, I pulled lightly on it to follow what it hooked up to, and the end of it was not connected to anything, its 100% corroded and broken off from something. I followed it back the other way and sure enough, it goes to the alternator. Where should this wire hook up to? I looked around briefly but did not see a connector on anything that it could have broken off from.

Great call by the way Bt Doctur, huge step in the right direction.

Where exactly is the wire supposed to connect?

 

[Eric 3.7LX Alpha 1]

Re: Replaced alternator, battery still not charging

It connects to the same terminal ON THE STARTER that the (+) red cable from the battery does.

The Orange on the alternator is the (output) terminal. It will charge the battery back up when the engine is running thru the starter terminal.

Be careful... to disconnect the battery first, and ensure the cable ends at the starter don't touch the other cable ends on the other terminals.

 

[natureschild88]

Re: Replaced alternator, battery still not charging

Just to double check and make sure I don't screw this up royally...

There are to terminals I'm seeing. One has a yellow/red striped wire. The other has 2 larger red wires (battery +?)

I should connect the orange wire to the same terminal as the 2 red cables, correct? I just want to make sure because I don't see an extra connector there that the orange wire could have broken off from. But for all I know it could have corroded away to nothing.

So connect to the same terminal as red cables?

 

[Eric 3.7LX Alpha 1]

Re: Replaced alternator, battery still not charging

Here's a link to Service Manual 7 for you engine, the factory Mercruiser repair manual

Boatinfo - Mercruiser Service Manual nr. 7 - 1983-1993 - GM V6 Engines

I'll post the link to the wiring diagrams for you in a second....

Section 4E Wiring Diagrams:
Boatinfo - Mercruiser Service Manual nr. 7 - 1983-1993 - GM V6 Engines

the diagrams get tough to read at the starter.... to confirm it, start the engine and meter that orange wire while it's still disconnected at the starter end, you should be somewhere between 13 and 14 or so volts engine running.

 

[MH Hawker]

Re: Replaced alternator, battery still not charging

Start at the alternator with a volt meter and see where you lose voltage.

 

[fixnfly]

Re: Replaced alternator, battery still not charging

The alternator should put out around 14-14.5 volts. Agree, check there first.

 

[bruceb58]

Re: Replaced alternator, battery still not charging

Make sure there is voltage at the field terminal and sense terminal and measure voltage at the output terminal of the alternator and battery terminal.

Without performing these steps, you are spinning your wheels.

 

[airshot]

Re: Replaced alternator, battery still not charging

Your fresh charged battery should last for more than 4x starting your boat unless your boat is very hard to start. A fully charged battery of the proper size on a good starting motor should last for many more than 4 startings. You should also check for some type of current draw down as something is draining your battery fairly quick. A lot of good info was suggested here but do look into other drain problems after you get the charge problem fixed.

 

[Bondo]

Re: Replaced alternator, battery still not charging

Any ideas?

Ayuh,.... Just 1,.... Post yer question in the 1 forum that it Best fits in,....

Not Every forum it might fit in,....

Multiple postin' just creates massive Confusion,....

Thank you,...

 

[achris]

Re: Replaced alternator, battery still not charging

Just to double check and make sure I don't screw this up royally...

There are to terminals I'm seeing. One has a yellow/red striped wire. The other has 2 larger red wires (battery +?)

I should connect the orange wire to the same terminal as the 2 red cables, correct? I just want to make sure because I don't see an extra connector there that the orange wire could have broken off from. But for all I know it could have corroded away to nothing.

So connect to the same terminal as red cables?

Yes....

To other posters.... Please read ALL the posts in a thread before posting. Many of you have posted, after the discovery that the orange wire was broken off, suggesting to do things like checking the voltage at the alternator.... if you had bothered to read ALL the posts you would have found that the OP has already done all those things... and more!!!

Very frustrating (both for me, and I suspect the OP) to read through suggestions that are no longer relevant...

Chris...

 

[bruceb58]

Re: Replaced alternator, battery still not charging

f you had bothered to read ALL the posts you would have found that the OP has already done all those things... and more!!!

Please locate the post where he measures the voltage at the sense or field connection or is this no longer relevant? :facepalm:

 

[achris]

Re: Replaced alternator, battery still not charging

Please locate the post where he measures the voltage at the sense or field connection or is this no longer relevant? :facepalm:

I would say that the orange wire broken off its connector would render this irrelevant for the moment, yes...

If the problem is not solved when the orange wire (the main output of the alternator) is reinstated, then start troubleshooting using other suggestions. But until the output of the alternator is connected to the battery, then everything else is moot....

Chris...

 

[natureschild88]

Re: Replaced alternator, battery still not charging

Got back to it this morning. I took all of the wires off of the corroded terminal and cleaned everything thoroughly. In the process, the red cable (battery +) broke free from its connection in the same manner that the orange one had already done. Completely corroded.

I put new connections on both the battery cable and the orange wire and hooked everything back up. I turned on my chart plotter and it read the battery at 11.6 volts with the motor not running. When I started the motor, this number jumped to 13.7!! Success! :clap2:

When i revved up to 1500 rpm the volts rose to 14.1. When I shut the motor back off (after running it for less than a minute) the battery was reading 11.8, which tells me it charged!

My only concern is that when I initially turned the boat on, I had the chart plotter (Humminbird 597 HD DI) running. When I turned the key to crank the motor, the screen went white and did not go back. I had to unplug it to turn it off. After I plugged it back in and turned it on it ran fine.

It has never done this before, and this is the first time I had it running during engine start up with a properly working alternator. Should this be a concern? Any ideas as to what could have caused this? I have a fuse inline with the wiring on the unit.

Anyway, the alternator works and I'm ready for an awesome vacation up in the Sierras. Thanks for the help everybody!