[dhoward]

Should read a little over 12 fully charged. Is it a deep cycle marine? Did you check the electrolyte levels? Low electrolyte will give a slightly lower voltage reading. Manualy cycle the pump a few times, disconnected from the house current. See what the performance is like. Does it start to slow down quickly? Usually a sump pump runs on a short duty cycle, just long enough to empty the sump. Then waits 'til it fills again...