My alternator produced up to 16 volt and was very hot.

[nennedk]

Yesterday after 2 hours run with cruising speed, we stopped, with engine off, for about half an hour, just outside out harbor. The last run into harbor i gave it full throttle and trimmed the drive. Just when I pushed the trim button all electricity disappeared for a short moment (my Chartplotter shut down). I throttle down to cruising speed and tried the trim again. And the same happened again. I throttle down to around 650 rpm and turned on my chartplotter again. I noticed that the it was reading 12,5 volt, and is usually 14 volt all the time from 650 rpm to 4500 rpm. I tried the trim again and now it worked without killing the electricity. But as soon as i gave it a little throttle the chartplotter told me 16 volt. I could get the chartplotter voltmeter to fluctuate between 12,5 to 16 volt depending on the speed. The built-in volt meter however did not, it stayed at 13.5 volt (it also usually shows 14 volt). The alternator was very hot without knowing how hot it used to be, but it did smell hot to.

Both voltmeter did settle down at last, showing the same and not going over 13.5 volt.

Can anyone tell what is going on and if should i be worried? Thanks.

My engine is a Mercruiser 5.0L carbed from 2001. SN 0M359543

 

[Bt Doctur]

bad batery causing overcharging? Bad alt starting to go wild?

 

[nennedk]

The battery is a Varta 105ah from 2014 kepped on trickle charged over vinter periods, I think that is a bit early but who knows. Can I check it somehow? Can i check the alternator?

 

[Scott Danforth]

check your sense connection (ignition switch connection - purple wire) to see if you have corrosion. if you do, fix it. if not, the alternator regulator may be going.

 

[vetplus40]

I'm fairly new here, but I was wondering if the alternator could not be checked at an Autozone or some place like that?

 

[alldodge]

I thing the since lead (Red/Purple) has a break in connection. The Orange and Red/Purple should be battery voltage full time. The Purple supplies 12V from the key to turn the ALT ON.

I'm fairly new here, but I was wondering if the alternator could not be checked at an Autozone or some place like that?

It could be done but there is no one that is smart enough to figure out how. They have to follow how the machine tells them to do it, but there are no instructions for a marine ALT

 

[Scott Danforth]

take the alternator to a real alternator/starter repair shop. the people that work at autozone do not impress me with any automotive knowledge.

 

[nennedk]

Went to the boat today. As told it used to be steady at 14 volt at all rpm range, but now it starts with under 12.5 volt. I then rev a little to get it started and then it will be at 13.5 volt. It will stay there as long as i'm under around 1000 rpm. Above 1000 rpm it goes up and up until 16 volt. Already at 1400 there is 16 volt.
The battery shows 12.8 volt without engine running, so I think it's ok. There is no issues in cranking the starter and starting the engine. My conclusion is that the alternator is giving up.
The alternator product no. is 863077-1. Should i go for an original, reman. or a Sierra?
The price here in Denmark is $589, $374 and $483 accordingly.

 

[alldodge]

The ALT does not normally go high unless the sense lead is disconnected or a bad connection. So far as which to replace with any will work, but I would go org or reman

 

[nennedk]

None of the 4 wires have corrosion, but if I should double check the sense wire what is the best procedure? Thanks in advance.

 

[alldodge]

Check that the Orange wire and Red/Purple wire show the same voltage. Pull the plug off the ALT and check the pin for the wire in the plug, ground negative meter to ALT body

 

[nennedk]

Ok, with ignition OFF, there is 12.62 volt at both orange and Red/purple and 0.05 at purple. With ignition ON there is 12.57 at both orange and red/purple and 12.44 at purple. Its the same numbers weather i'll ground at alternator body or batteri negative pole.
Anything i can meassure with engine running?

 

[wellcraft-classic210]

Hi

I had a rebuilt one one on an auto that went high got hot -- some sort of diode fail in the regulator or internal short -- replaced it and problem gone -- Your problem may differ but it could be the alternator internal parts

-- and going too high on voltage can definitely damage components as it raises the current through them.

 

[nennedk]

Yes, I now also believes it's the regulator/diode fail. High volt, very hot, smell burned. I will replace it and hope that solves the problem.

 

[alldodge]

OK, ALT regulator is bad

 

[nennedk]

My locale boat pusher had a remanufactured alternator on stock, so bought it, installed it and now everything is fine again. I really appreciate your help in here. Thanks again