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At the voltage regulator. If you have loose or corroded battery connections, that'll take it out. So will accidentally connecting the battery backwards or switching a battery switch (if your boat has one) while the motor is running.
The other major component is the stator under the flywheel. The charging part of those hold up pretty well. The vast majority of charging problems are at the regulator, but a bad stator isn't impossible.
Not charging 1993 mariner 115 4cyl.
Linear Mode
