mercruiser alternator questions

[jopes]

88 vintage 305, alpha 1.

the problem is it does not like to charge @ idle. Now today coming off the lake it was only putting out 12.3 volts which is not enough to charge the battery from everything I have ever known. bringing the engine rpm's up did not increase the voltage.


Has my alternator given up on me or is this normal for them? Turning on accessories only brought the voltage lower.

 

[HT32BSX115]

Re: mercruiser alternator questions

Howdy,


Well,

After you check all the engine ground and positive connections, you might remove your alternator and drop on over to Autozone, Napa, or other autoparts store and have them test it.

They'll test the alternator on their test fixture and will be able to tell you if it's failed.

Regards,


Rick

 

[Bondo]

Re: mercruiser alternator questions

Ayuh,... Generally speakin',...
Once they've made a run up of rpms, alternators will put out full power at idle...

Grab a multimeter, 'n Look to see where, 'n what the power is before rippin' it off, 'n replacin' it...

 

[dubs283]

Re: mercruiser alternator questions

you might remove your alternator and drop on over to Autozone, Napa, or other autoparts store and have them test it

why go through all that trouble when he can test it right there, in his boat??

follow bondo's advice and grab a volt meter and with the engine at about 1500 RPM check voltage at the battery, the output stud on the alternator, and the back of the guage - you will know what the alternator is putting out

 

[jopes]

Re: mercruiser alternator questions

guess I will grab the ears and hose tomorrow and see what it is doing.

 

[fishrdan]

Re: mercruiser alternator questions

Do as Bond-o suggested to make sure it's the alternator.

My alternator was doing the same thing, 12.3>12.5V was about all it was putting out at 2K up to WOT, off idle was pretty much nothing. I replaced it with a new (China copy-cat) from DB Electric and it's working fine now. Get it to about 1200RPM and it will cut-in and start charging, even if you drop it back to idle.

I'll troll off the main to charge my trolling motor batteries back up...

 

[Don S]

Re: mercruiser alternator questions

Might want to do the testing from this Merc service bulletin before you take it apart.

Service Bulletin 2001-12

 

[dubs283]

Re: mercruiser alternator questions

Merc service bulletin

read that bulletin

wow...remove and replace if still under warranty

what ever happened to troubleshoot and repair??

 

[jopes]

Re: mercruiser alternator questions

Might want to do the testing from this Merc service bulletin before you take it apart.

Service Bulletin 2001-12

Thanks for that bulletin, I will print it out and follow it tomorrow to see whats going on.

 

[Don S]

Re: mercruiser alternator questions

what ever happened to troubleshoot and repair??

When I started working at the place that I just retired from, the normal procedure if someone had a charging problem was to order an alternator before ever looking at the boat. That stupid habit stopped when I started working there.
This was "The best place to go for repairs' when I was looking for work. the place scared me, because i didn't think places were that bad. I was wrong.

 

[dubs283]

Re: mercruiser alternator questions

order an alternator before ever looking at the boat

if i did that i would be laughed right out of the shop!! (along with my tools)

 

[HT32BSX115]

Re: mercruiser alternator questions

why go through all that trouble when he can test it right there, in his boat??

Aside from following the procedure in the above Service Bulletin,

Most electrical problems in boats are due to corroded connections, loose wires, loose/corroded crimp connections, loose grounds, etc.

It might be nice to know if the alternator is actually working(because they're frequently NOT faulty) independent of the boats electrical system before troubleshooting the rest of the electrical problem.

 

[dubs283]

Re: mercruiser alternator questions

Most electrical problems in boats are due to corroded connections, loose wires, loose/corroded crimp connections, loose grounds, etc.

agreed, i was not arguing that point

It might be nice to know if the alternator is actually working(because they're frequently NOT faulty) independent of the boats electrical system before troubleshooting the rest of the electrical problem.

and if he follows the advice of bondo, which i concurred with, he will know

i find it needless to have someone remove an alternator and drive all over town to have someone who may or may not know how to properly test an alternator

i have heard guys at NAPA actually say,"we can't test a marine alternator, only auto" - that tells me they don't know how to properly test an alternator

 

[jopes]

Re: mercruiser alternator questions

i find it needless to have someone remove an alternator and drive all over town to have someone who may or may not know how to properly test an alternator

i have heard guys at NAPA actually say,"we can't test a marine alternator, only auto" - that tells me they don't know how to properly test an alternator

on a side note about that one. I had pulled a older alternator from a ford Thunderbird to specifically make a welder out of it. The counter person took like 25 minutes to figure out how to test it and get all the wires hooked up. First few tries he had the wrong wiring. After finally getting everything correct, he said the alternator was putting out the proper amps but the voltage was too high and was defective. After I thanked him and said it would work just fine, I think he was a little saddened that I was not going to be buying another alternator from him.

 

[jopes]

Re: mercruiser alternator questions

Put it on the ears and took it to 1300 rpms and the voltage was 14.3, This was @ the terminals on the battery and the in dash meter showed 14 volts. Checked the diodes with the AC part and they were about .10 VAC.

I am just going to carry my meter with me in the boat and the printed directions and see what it is doing if the voltage drops again.

 

[HT32BSX115]

Re: mercruiser alternator questions

i have heard guys at NAPA actually say,"we can't test a marine alternator, only auto" - that tells me they don't know how to properly test an alternator

I can't comment on the idiots at your local Napa...... The SEVERAL alternators I have had tested at the local Autozone or Shucks didn't require me to "drive All over town" and I didn't tell them what they came out of before they tested them.....

 

[Bondo]

Re: mercruiser alternator questions

Most electrical problems in boats are due to corroded connections, loose wires, loose/corroded crimp connections, loose grounds, etc.

Ayuh,... Especially the Grounds, 'n continuity straps....

I like My electrical connections scratched to shiny metal, assembled, tightened, 'n slathered in a fingerfull of Grease...

As fer drivin' All over the county to get somethin' Tested,...

That what a $20. Multimeter is for,...
On the equipment, boat, car, tractor, Whatever....
'ell, 1 of the chinese 1s from the dollar-bin will do the job, atleast Once,...
Well, maybe once....

 

[jopes]

Re: mercruiser alternator questions

I had the ears on it yesterday and it tested out just fine when putting out a charge.

Today out in the boat after a while of running it stopped charging. So I broke out my printed tech bulletin and followed it. Everything was getting power like it was supposed to.

So I was sitting there thinking and I grabbed a wrench and lightly tapped the regulator on the back of the alternator and it started charging, then stopped, tapped it again and it started charging again and charged for a while. Drove to the next fishing spot and when I restarted the engine again it was not charging. Then after a bit of running it charged up, then stopped yet again.

It possible the regulator is flakey under heated conditions?

 

[Lyle29464]

Re: mercruiser alternator questions

might be junk underneath warn out brushes. You just help them seat for a minute when you knock the junk loose and help the springs.

did you notice no magnetic pull on your wrench when it was not charging and a strong pull when it was? saves a trip to the parts store.