alternator problems

Xplicitlnck

Xplicitlnck

Well-Known Member
Jan 2, 2012
4,030
Long island ny
Boat Info
330ec
Engines
Twin 7.4 straight drive
Ok well I guess im still having charging problems. I changed my batteries and alternator due to no charging. It wnded up being a dead alternator. After changing the alternator everything worked great 14.5v at cruise. After spnding the day on the hook I started my short journey home and about 15min into the trip I noticed what seemed to smell like and electrical fire. . Shut everything down went I to the bildge and the brand new alternator that I just installed was the culprit of the smell. What could be causing my boat to eat Alternators or am I just adding to my unlucky streak by buying a bad alternator? Its still putting out 14.2volts but my batteries wont go over 13. I put the multimeter on the batteries and then started the engines and it jumped from12.2 to 13 volts so I know the wiring is still good. Very frustrating. And ideas (the alternator is a "brand new" sierra they said it was not rebuilt)
 
Follow the wires from both alternators to the bulk head they should go into a equalization box. On my boat it looked like a mini charger. It is a diod system that allows one alternator to charge the battery on the opposite engine. Feel it if hot in may need replacing. I got mine replace by an electian. Sorry can tell you more but it could be part of your problem. The electitian said the old ones cost you up to 1.5 volts in charging power from your alternator. All to complicated for me. When I replaced my alternators I put in 70 AMP ones rather than the 55AMP ones that came with the boat.
 
Nothing like bucking Alt`s against each other. Is there water in the batteries? What type of batteries?
You should have 2 INDEPENDENT SYSTEMS isolated from each other.This way something bad happening cant transfer over to the other engine.
Twin engines with current wiring, you going off shore 100 miles. Systems read good at start up(14.6) but unknown to you only 1 alt is working, the other is dead.You cant tell because the voltmeters read the same.
You arrive and shut down , dead alt draws backdwards and kills both batteries. Have a nice day.Radios dont work with dead batteries.

Back the the original question, you cant read 14 at the alt and 13 at the battery unless the wiring has issues like hi resistance or some kind of isolator device.
Spend a couple of bucks and rewire it to a true dual engine setup.This way if 1 goes bad you`ll know right away and still have the second to get back.The manufactures are a bit cheap in the battery,battery switch depeartment.
 
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Very frustrated. Well I def need another new alternator cuz mine smells like charred wires. As for the wiring i ill go down and c heck all connections and c if a ything is getting to hot..... ill keep ya posted and thnk you
Thanks computer man just sent him. Pm
 
Bt Doctur said:
Nothing like bucking Alt`s against each other. Is there water in the batteries? What type of batteries?
You should have 2 INDEPENDENT SYSTEMS isolated from each other.This way something bad happening cant transfer over to the other engine.
Twin engines with current wiring, you going off shore 100 miles. Systems read good at start up(14.6) but unknown to you only 1 alt is working, the other is dead.You cant tell because the voltmeters read the same.
You arrive and shut down , dead alt draws backdwards and kills both batteries. Have a nice day.Radios dont work with dead batteries.

Back the the original question, you cant read 14 at the alt and 13 at the battery unless the wiring has issues like hi resistance or some kind of isolator device.
Spend a couple of bucks and rewire it to a true dual engine setup.This way if 1 goes bad you`ll know right away and still have the second to get back.The manufactures are a bit cheap in the battery,battery switch depeartment.
Click to expand...

I agree!!! If the wires are original to the boat or even a few years old I could see an issue with corrosion hence a high resistance.
 
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Ok I just off the phone with the prev owner and asked him if he ever had any charging problems.the only thing he says he ever noticed was the volt gauge on the dash would surge up to 16.2-.5once in a while. Would surge for 20sec or so thn go back to normal..... I may have noticed once but not to sure if im making myself notice something that didn't happen or if it actually did. What would cause that..?
 
Ok new questions.
1 cana belt thats maybe a little to tight cause an alternator to blow?
2 I bought a new mm how do I use it to check resistance.
3 I know I know I went cheap and bought my alternator from ebay for 70 $. Prob a good chance it was bad out of the box? But it did work for 2 hours of run time and the output is still reading 14 v. Could I have just fried the bearing because the belt is to tight?
4 if the alternator is putting out 14v how long will it take to get the batteries from 12to 14 @65amp output?
Im going out tomorow to check all the wires for corrosion again. Gunna pull all the zip ties and loom off this time. Other than wires and connections what else could be causing this?
I know im redundant but I neex to fix this. Big trip coming up and need to know or atleast think im safe...
Bt doc
I know you sent me your cell but I need to ask if I don't find anything tomorow can I call u for some assistance and if yes ill b there after 4 is there a good or better time to call?
Comp man
U don't know the guy selling the power supply do you? He never answered the pm or ad he posted?
 
anything over 14.6 means the alt is "running wild" that means the alt is not connected to a battery source or the alt regulator is bad. you should also check the neg wire connection to the alt case. dont depend on the mounting bolts to supply a good ground.
1 no ,causes the front bearing to self destruct
2 turn it to the "ohm`s setting and read the corosponding scale R X 1, R X 10, R X 100, etc.
3 yes
4 varies on the condition of the battery,doubtful you could charge at 65A without destroying the batteries
If all else fails all you need to do is remove the existing wire from the alt output lug and run a new #10 from the output lug directly to the +
battery post
call anytime
A crude batttery cell test is to put the meter on a low voltage DC scale, black lead to neg post, attach a short piece of copper wire to the red lead and carefully insert it into the acid of each cell.
read each cells voltage.Now put the red meter lead to the pos and use the black lead to dip the acid.Record the readings. 6 cells x eg:2.2 volts =13.2
neg on the power supply.
 
Your the best. You may hear from me tomorow. If not I probably found something and either fixed it or think I. Fixed it. Thanks for the help.
 
Ok just finished up. I found nothing wrong with any wires. All connections are good and starting with no corrosion on any wires anywere.
So i changed out the alternator again and put myoriginal batteries back in and fiered up. I got. 12.7 volts and slowly climbed to 13.1.
Went for a ride for about an hour and my readings are as followed
Idle. 12.7
1000. 13.1
1400. 13.1
3250 13.3
Then when backing off
2000 13.3
1000 13.5
Port was always .5v higher than star...
Normal? Not normal?
I dunno what else to do.
When I rev up star motor port and star meter jump up when I rev port nothing really happens just a small jump maybe .2 v...
 
The first is a starter solenoid, thats your emergency start solenoid, helm switch is attached to the lead into that solenoid. The other appears to be the isolator, it appears there is a label inside near the connections. Isolators are diodes that isolate the batteries from each other to reduce the chances that batteries will drain down by backfeeding voltage into another battery.
Isolators are well know for affecting the charging system, and at time eating up alternators.
 
Supposedly there are new isolators that are solid state instead of just a diode pack. I'm not sure how old yours is, mine looks different. Yours may be a newer style. I would have to do some research to find a way to test them, I have never really messed with mine.
I would never tell someone to replace something without thinking I had some knowledge of how to test it. I do know I have read other places that people have noted that they will cause charging problems.
Seeing that I have never really looked into how they actually work, and how newer models have supposedly improved, I am also interested in finding out more about them as well.
 
Well im fed up with searching so im just gunna change it and c what happens. Ill let you know later on.I did a little research and cMe up with a bad isolater showing the same symptoms as im having
 
Dude, sorry you are havin so many problems. This is bordering on ridiculous now... I think my black cloud has moved to you or just got really big and now encompasses both of us! Lol
Good luck, I hope that's the problem.


Sent from my iPhone using Tapatalk
Todd
 
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