2005 merc XR6 alternator output????

[marlake]

Brought my Nitro NX882 w/ 150hp Merc to Florida again this year for 3 months of bass fishing (yes, I'm braggin.)
Just noticed since I've been here that the voltage gauge has been showing 14 to 17 volts output from the alternator. This seems a bit much and I'd appreciate some ideas as to what might cause this excessive voltage, what damage is being done by running this way and, what I can do to fix it myself. It's impossible to get a boat shop to take me in for repairs and get me back on the water quickly. Just too busy they say. FYI, I just installed a new starting battery on January 5th 2022. Don't know if this has any possible effect but I thought I'd mention it.
Thanks in advance for any ideas you may have.

[Bud Kennedy]

That output voltage sounds about right for that motor.  Just what do you think it would be?

[marlake]

The voltage reading I've seen in the past run between 11 and 14 volts. My understanding is that a properly functioning alternator delivers 12v to 14v. Now, having said that, I'm realizing that the readings I'm looking at are from the voltage readout on my Humminbird Helix 7. I don't know if that Humminbird readout has anything to do with my Mercury XR6 charging system. The Humminbird readout is, probably, telling me that there is sufficient voltage for the unit to perform its various functions properly. I only know that the readings are higher than they had been in the past and am wondering if they are signaling an upcoming problem.
I'm just guessing and still welcome any ideas.
Thank you.

[Mike Cork]

I'd definitely get a volt meter and test the system versus trusting a gauge or the Helix.

If you are hitting 17 volts, while that might be with in limits it does seem a little high, especially if it's staying that high and not just achieving it to help with strains on the system.

[marlake]

Thanks for the response Mike. The voltage readout from the helix will vary with the increase in RPM running between roughly 12v and topping out at 17v at around 3500 rpm. I'm going to pay more attention to the gauge in the dash of my boat and see if it is giving similar readings. I would think that would be more reflective of my Merc's charging system.
I have a volt meter. What do I hook up to so I can get a reading?

[Bud Kennedy]

Just wondering if you may have a voltage regulator starting to head south.  Seems logical to begin your measurement at the output of your battery and then move to the voltage regulator.  Interesting problem for sure.

[Mike Cork]

I'm with Bud. This will take two people, one driving and one reading. Or you can try on the trailer at a ramp. Hard to reach 3500 RPM on a trailer.

But I'd check at the battery first to verify everything. Unless there is quite a load on the system I just don't know why the system would put out 17 volts unless the regulator was going bad.

[marlake]

Thanks again for the input, guys.
About 6 months ago I bought a pair of regulators/rectifiers to have "just in case". I'm gonna install them tomorrow and, after my next trip to the water, I'll report as to whether or not there is an improvement.
Just out of curiosity, what could/would be damaged by continuing to run with the high voltage delivery I'm now experiencing? I'm fairly mechanically minded but an electrical moron.

[Bud Kennedy]

Not being very familiar with your motor, I have been researching this problem.  I see recommendations that certainly indicates a regulator issue.  It is recommended they be replaced in pairs and it is also recommended to use Mercury parts and not aftermarket stuff.

Other damage could include the Stator and very possible the power pack itself.  I would think anything within those control circuits could be impacted.  Hopefully the regulator replacement will cure your problem but you should approach the other issues as "next steps"

[D.W. Verts]

What was said above. Also, check ALL connections, clean, tighten, etc. I know that sounds backwards, but do it.

Dale

[marlake]

I replaced both regulator/rectifiers and that fixed the problem. Voltage reads between 12v and 14v during normal operation. Thanks to all for your input. Much appreciated,

GONE FISHIN       

[Bud Kennedy]

good deal.  Glad you could resolve the problem.