My propeller was vibrating rather strongly when motor sailing in non-flat waters.  Such vibration was only felt during certain parts of the up and down motion with the waves.  In Martinique, the boat was taken out of the water to tighten the rubber bushing the links the C-drive with the keel.  It is a rubber sleeve with ~ 7/8" ID and ~40 mm OD and ~35 mm long.
  They told me that all they needed to do was to tighten the bolt that would squeeze the rubber tube expanding it and eliminating the play.  Actually, the rubber sleeve  was already squeezed at max and had deteriorated to the point that it was allowing motion even though the bolt was tightened at max.  Unfortunately, Amel did not have with them a replacement and they made one by wrapping silicone rubber tape around a plastic tube.  This reduced the vibration but it was still noticeable and I was concerned the rubber was going to disintegrate with time.  
So I am now replacing it with something that should last the rest of the boats like.

MY QUESTION IS:  does anybody have the exact dimensions of the rubber tube (particularly the Length) and the material it was made of?

Jose Venegas
Ipanema SM 2K 278
In Cartagena de Indias (Colombia)