If it has no regulator, then that would be normal. I am not a OMC guy but that was normal for older merc’s.

I was always under the impression that the OEM alternators were only 7 amps and COULD’NT put out that kind of voltage thus they only had a small rectifier. Not sure what amperage the CDI stators are but can’t be that much bigger can they? Have you tried a different volt meter?

The rectifier that came with those motors did not provide any voltage regulation.  However, CDI now makes a REGULATED RECTIFIER for people that just stand to see 16V as normal.  BTW, the factory service manual says to just turn on some lights.

I had an old 1971,125 hp Johnson, that used to do the same thing. Back then, there WAS no optional regulator.So, I used to watch the voltage and run the power tilt in the down direction, occasionally to knock the voltage back down. You just need to add some more fishing equipment and lighting, to get it under control. You probably only need to find about five more amps. (You have the opposite problem from the Apollo 13 crew!)