1982 Mercury BM 150hp sn# 6101202

So i have a 1982 BM, i recently put battery voltage on my lowrance screen & have noticed at idle / low rpm the system is putting out ~13.7v via lowrance. But at higher rpm it's 15.x V

I get that the flywheel with magnets is spinning around the stator, creating juice.

I'm unclear of the rectifiers job & how it's involved.

How does the electricity get funneled back to the battery? Which wires? How should it be routed back to the battery / what is the proper wiring route?

How does the electricity get regulated? Does it? Is the stator made to only produce a certain amounts of amps?

The cdi unit i installed is claimed to be a 9amp unit.

I tried watching a few utube vids, but my questions werent answered.