Sounds like automatic car door locking and unlocking

[senormechanico]

My bet's wiring slapping in the mast. Turn off the electrics at the battery to eliminate any electrical activity.
At that point, it would have to be a mechanical type of sound if not sea life activity.

[mvmojo]

Could be polyester mites eating the hull! That's what we used to jokingly call snapping shrimp frequently heard while at anchor. Lots of little clicking noises. The first time I heard it I went crazy trying to find the noise.... but it was everywhere! Finally just went back to bed and didn't worry about it. Was later told about the snapping shrimp eating the algae off the bottom of the boat.

[Hesti]

It can be the fenders. When the boat is moving a bit, the fenders can start to bang against the hull - if you have hung them. Then, even small waves can slap against the hull.



Running rigging and electrical cables have already been mentioned.

[Capt Gill]

Originally Posted by Freedom45

Do you have an automatic battery combiner?
My old boat had one with a relay that would clunk when activated.

+1 My batt. combiner sounds exactly like cycling auto door locks.

[Howler]

When you turn on the battery switch for a windlass, bow thruster or electric winches (assuming you have any of these), it makes a sound like an electric car door lock. If there’s a faulty switch and one of these is going on and off by itself, it could explain such a noise, but it would be localized and not all over the hull.

[RSB333]

We're all waiting to hear what it. Let us know when you find it.
Cheers!
RSB333

[Wayne hoath]

Originally Posted by Capt Gill

+1 My batt. combiner sounds exactly like cycling auto door locks.

+1 Yep. My xantrex pathmaker makes this sound when it switches. Not constantly. Possibly the answer if you have automatic battery switching?

[skipper53]

Consider checking for rudder slap caused by a worn bearing or bearings. Mine are due for replacement and can be heard very clearly when the boat rocks a bit even in the slip. We're out of the water now and this project will be completed before Spring launch.
I was surprised to not feel this in the wheel but can move the rudder back and forth by hand in any direction when standing on the hard.