Boiling Battery

OK, hears one that has me stumped

91 Plymouth Laser 1.8l SOHC Constant clear liquid around the battery, especially around the top vents, very corrosive. No, the battery does not have a leak. Battery was three years old, exchanged with another three year old battery, same thing, clear liquid around battery. Constantly adding water to the battery. Removed regulator from the car (It's inside the alternator), set it up on the test bench, regulator turns on (alternator) at 13.8 volts and turns off (the alternator field winding) at 14.2 volts (at about 70 degrees F). Battery voltage measured at the alternator/regulator, is the same as the voltage measured at the battery. This vehicle uses a separate sense wire to measure the battery voltage for the regulator, tests OK (same voltage at either end of the wire). With the car running, the measured output voltage of the alternator is 14.2 volts. Manual says voltage should be between 13.9 and 14.9 volts Question is, why am I boiling the batteries. Car runs fine, starts OK, no other problems. Can it be I have two bad batteries.