I'd had a recent issue with one of my Odyssey AGM batteries where it just appeared to be dead, it's only 2 years old but was showing 10.6 volts one morning. I had been running on this battery all day, coved out for several hours, came back home and everything seemed normal. So, I plugged in my onboard charger, left it on and checked the battery after a few hours, maybe 11 volts or so. So I was convinced the battery is dead, but no replacement available at the lake, just decided to run on the other battery the next as we had some friends coming down. Got done with the day, plugged the charger back in and...the next morning the battery showed full charge. During my research it was noted that AGMs take a higher voltage, 14.4, to get a full charge...I am really simplifying this...and it got me to thinking that I have never seen 14.4 volts on any of my gauges or displays...13.7 is tops, usually around 13.3. So I am wondering if my stock Mercruiser 65 amp alternator has an issue? This is the first time I'd had this happen, I am 90% sure I didn't leave anything electrical on to run the battery down...perplexes me.

Does anyone ever see 14.4 volts? It is my understanding that is the max the alternator can/will put out.

Check your voltage at the battery itself as you're probably losing at least 0.5v to the gauges. I have 5 yr old duracel AGM's that are going strong on a similar setup to yours but I do top off at least once a month with an AGM charger.and/or before every time I fire the engines.

X 2. For proper charging and etc diag, Always ck voltages at battery