The hose in photo number 4 (labeled tank vent), is NOT a tank vent. It is a hose that exits at the inboard edge of the the aft locker under the table in the saloon.  

If you look closely in the picture, and you can check this on your own boat, you can make out that there is an electrical cable inside the hose.  I asked Olivier about this hose when we took deliver y of the boat and he indicated that the hose was there to protect the cable inside, and that cable is the sonic speed indicator sensor/transmitter that is imbedded in the leading edge of the stub keel (i.e. the lower aft transducer of the two sonic speed transducers). At the forward end of the hose the cable exits and traversed starboard to route to the sonic speed computer that is strapped under the shelf in the forward lower cupboard beside the starboard side saloon seat.

Olivier, if you see this, can you shed some light on how it might be possible (or not possible) to replace the sonic speed sensors (both in the stub-keel and the forward hull).  It seems many of us have had failure of the transducers.  Are the sensors in some sort of conduit that allow them to be pulled and replaced?  

All the best, 

Gary Silver

s/v Liahona  

lying Sapphire Bay Marina, St. Thomas,  USVI