Re: 75hp merc voltage problems
Give me the CDI part #'s for stator & rec/reg. Here's how older merc charging systems worked: The stator, generally a 9 amp unit, puts out an AC voltage on it's 2 yellow wires that vary in voltage (and frequency) according to the motor RPM. This AC is converted to DC by way of the rectifier which is 4 diodes in a "bridge" configuration. This voltage also varied as to the RPM. Merc's original design used the fact that the battery acted as a load always taking a few amps even when charged. This few amp draw shorted the output of the low-amp stator enough to cause almost "auto-regulation" of the charging system output, hence many of the older motors had no regulator. With battery technology improving (less full-charged draw) and the need for more amps because of all new the marine electronics available, the motors started coming with bigger stators and the battery couldn't self-regulate anymore. Merc started putting on a regulator that would sense the DC voltage from the rectifier and short one of the yellow stator leads to ground when the voltage got too high. This along with the battery draw would keep voltage constant. Problem with this is if a battery post loosens and doesn't take some of the extra amps, or you put on a CDI high-output stator, that sorry regulator has to do overtime work and fries! CDI makes a great unit #194-5279 that rectifies and regulates, not by shorting out the yellow leads but electronicly by just shutting off the charge circuit when the battery voltage is at 14 where it should be. This keeps the stator much cooler also. Hope this helps.
