Joel and Bill have answered your question and I concur that my Maramu has a drain hole at the bottom of the rudder as well.  I would only add that on my Maramu that after hauling the boat, I fill and drain the inside of the rudder with fresh water a couple of times to try and remove most of the salt.  I am careful to insure that the air vent in the top of the rudder is open so that the rudder does not develop internal pressure from filling the rudder with freshwater.   My thoughts are that it is always best to remove salt where possible before storing a boat and thanks to the unique Amel rudder design this is one more place that can be rinsed.   I am curious if other Amel owners do this?

Best,

James Alton

SV Sueno,  Maramu #220