Too much voltage?

[NewNitro]

Ok, had a friend drive and me with my head in the bulge with a fluke meter. For my sake I had him run at 4500 rpm. Started out at 12.7 and by my watch within 7 minutes we were at 13.3 within a minute it went to 14.9 and just to satisfy my curiosity I had him keep going until it hit 15.9 and climbing ( about another minute). Couldn’t help but glance and noticed the graph read 14.4. It’s a pain to get battery out but taking it out after it cools down and taking it back to where I bought it for load test and hopefully a replacement

[EuropeanAM]

Unlikely that it is the battery, just to let you know.

Need to test the rectifier FIRST, and if it is good, the regulator would need to be replaced (note- as suggested earlier, this one is NLA now, meaning you're hunting leftover or used parts).

While I have not ever done it on THIS engine model, I suspect that the later-style regulator/rectifier would WORK (slightly challenging to mount, but should functionally do the job).

Have used it on several other "non-Merc" engines over the years with decent results.

WOULD require some wiring work and at least a moderate knowledge of the workings of a stator-type charging system.

[NewNitro]

Ok , thanks for the help, I’ll check manual on replacing the regulator. Battery is out, the store is an hour away so will go in the morning. I have the battery here that I replaced with this new one, I’m going to put it back in and see what happens in the meantime.