Name:   wix - Subject:   Boat noise with batteries off... Date:   5/25/2017 8:48:14 AM (updated 5/25/2017 8:53:58 AM)

Agree with all above.  You didn't say the boat is in a boat house, so, if not, it may just be dumping some of the 6" of rain we've had in the last week.  My guess is you have just enough water in bilge to trigger pump, pump tries to evacuate, and lowers level in bilge then shuts off.  Water in pump out tube runs back into bilge, which raises bilge level enough to trigger pump...again.  I've had it happen...vicious cycle.