99' Merc 250 EFI, lost charging voltage but then came back

[MakoNY]

Noticed my volt meter was low the other day, measured voltage at the battery with the engine running and was reading aprox. 11.5 which means not charging and it was probably drawing off the batteries, figured the alternator was shot, but went out today and looked it over, started it up and now it's charging fine, getting 13.5 at idle and 13.75 at high idle around 1800 RPM.

I did notice that the belt seems a bit loose, but it doesn't seem to be slipping and it's not squealing or anything, but when I watch it running it seems to be a bit wobble and there is some play in it, also I noticed a good amount of rubber dust on top of the alternator right by the pulley, so I assume the belt is wearing and leaving that dust. Belt looks ok, maybe some slight cracking, but not bad at all.

Does this seem like the alt starting to go or should I try tightening the belt and see what happens?


Thanks.

 

[MakoNY]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

C'mon, nobody?

 

[MakoNY]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Would an alternator that's on it's way out be the only thing that would cause this kind of problem? Does this engine have a separate reg/rec or is it all contained in the alternator?

Also I want to replace the belt, is this a belt specific to Merc and does it need to be gotten from a Merc dealer or can I just get the same size belt from any auto parts store?

I'm extremely new to Merc, this is my first one, so just looking for some input from Merc guys on here.


Thanks.

 

[MakoNY]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Isn't there any Merc pros that can tell me if this is the alternator, or if it could possibly something else?

I really don't want to pull the alt off and have it rebuilt just to find out it wasn't the issue, just looking for some input from guys who know Mercs.

Thanks.

 

[MakoNY]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Bump^

 

[MakoNY]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Really....nobody?????

 

[Faztbullet]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Check the connections at the alternator and the bracket also as these are know to come loose and break bolts, That alternator cannot be rebuilt as its welded together and the internal rectifier is made for Merc only..

 

[MakoNY]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Thanks Faztbullet. I checked the terminal on the alternator and it's tight and there's no corrosion, also looked at the green plug and it was tight and has no corrosion or anything either. I didn't specifically look at the bracket but it seemed to be on there pretty tight, but I'll look tomorrow.

Good thing you let me know it can't be rebuilt. I already spoke to a local guy that quoted me like $200 to rebuild it, wonder how he was gonna do that, haha.

Have you ever heard of an alt dropping out and then just working fine the next day? I mean I didn't go out and run it the next day, just idled at the dock for about 20 minutes but it was charging perfect...day before it wasn't charging at all.

Would my tach jumping around be any indication of anything?

Also is the belt a specific Merc dealer item ro can I just use any same size belt from the auto store?


Thanks for any help.

 

[Faztbullet]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Also is the belt a specific Merc dealer item ro can I just use any same size belt from the auto store?

If you can find the correct size go ahead.....

Have you ever heard of an alt dropping out and then just working fine the next day?

Yep.....

I already spoke to a local guy that quoted me like $200 to rebuild it,

For a extra $90 you can get a new one with 1 year warranty!!!!!
http://www.offshoremarineparts.com/3162m/prod_5690.html

 

[MakoNY]

Re: 99' Merc 250 EFI, lost charging voltage but then came back

Great, thanks for the help man.

What happens when the alt drops out and then starts working again, is it a temp thing? I was thinking that possibly heat caused the brushes to lose contact and then when it cooled down they made contact again, but that's really just a guess. Would heat affect the internal reg/rec at all?


Thanks again.