I own a 1989 Rinker Captiva 206 powered by a 5.0 LX Mercruiser Alpha One with about 600 hours. I’ve been having two related (?) problems. The first is that for the first several minutes after start up, the voltage drops to about 11.5 to 12 volts. After a few minutes it abruptly rises back up to 13+ volts where it should be. When this occurs, the RPM will drop slightly due to the increased load on the alternator. The second, more serious issue is keeping the alternator belt tight. It loosens up after only several hours and sometimes will break unexpectedly. The area near the alternator is always covered with black rubber dust form the worn belts. The pulley seems to spin freely and the pulley grooves are reasonably clean. The belts seem to tracking straight as well. It is still the original equipment alternator which is a Korean built Mando unit. Should I just spend the $200 to replace the alternator or can it be caused by something else? Also, do these alternators have built in voltage regulators? Thanks for the help.
