I recently acquired a 2000 Hunter 410. I have become aware of a sump box discharge system which discharges water on the starboard side of the hull. The water seems to just drizzle all the time. The external ring also has what appears to be rust on it. The water looks clean, but in little or no time there is a very dark rust like stripe down the side of the boat. Does anyone know what could be causing this? I have been instructed to leave the sump circuit breaker on all the time.