2005 Merc XR6 Alternator output?????

[Nitro 882]

Brought my Nitro NX882 w Merc xr6 150hp outboard to Florida again this year and I just noticed the voltage gauge on the dash shows the alternator is delivering as high as 17 volts when running about 3500 rpm. This seems a little much and I'm wondering what problem this might indicate and is damage being done to something in the electrical system. I've got another month of vacation in Florida and it's almost impossible to have a shop take my boat in and perform the necessary repair work quickly so I can get my fishing in as planned.

Can you guys tell me how big a problem I have and is it something I can fix myself?

Thanks in advance.

[cyclops2]

Load test the battery first.  Will tell a lot. At no cost at a major auto parts chain.

[Nitro 882]

Thanks, but I literally just installed a new starting battery the week I left for Florida (January 5, 2022).

[TnRiver46]

I’ve heard the rectifier going bad can cause this. Mine wasn’t putting out enough voltage but some of my amateur research indicated it could also put out too much voltage 

 

here’s a video of mine after forum member  @galyonjlocated and installed a new one for me 

 

[Way2slow]

I would suggest having the battery tested first.  We get new s***t that's bad all the time.  Next logical culprit would be the voltage regulator, those are only about $400 and easily damaged with a bad battery.  May have put off buying that new one too long. 

One second thought, since you just replaced the battery, make sure the connectors are clean and tight.

[Darth-Baiter]

On 2/27/2022 at 5:54 PM, cyclops2 said:

Load test the battery first.  Will tell a lot. At no cost at a major auto parts chain.

   Buy an inexpensive multimeter and see what voltage is at the battery terminals at revs.  Bare minimum you eliminate a faulty gauge.  
 

you don’t want to push too much voltage at a battery. In a car, it’s the voltage regulator,s job to limit how much the battery sees.  On my car.  13.4v.  A boat has to be similar.  
 

good luck.  I’d tow it into a car shop if I had to.  With a big tip in my hand.

[Nitro 882]

Just a quick update. I replaced both regulator/rectifiers and that fixed the problem.

Thanks all for your input.

[TnRiver46]

3 hours ago, Nitro 882 said:

Just a quick update. I replaced both regulator/rectifiers and that fixed the problem.

Thanks all for your input.

Good deal! 

[Way2slow]

Actually, to replace one, you usually have to replace both because normally, they are built into the same module.

A little gee whiz info.  If the tach quits working and it's not charging.  That's usually the Stator or the rectifier.  If the tach is working, but it's not charging, that's usually the regulator.  If the voltage is too high, that's usually the regulator but a bad battery or bad connection can cause it to be high.  A bad battery or one that will not fully charge will cause them to overheat and burn out. 

The worst thing you can do is jump one off (even in your car) and then expect the charging system to charge it.