Note inscription on bell...
It doesn't appear that bell is from JFKs' boat (or if it was in the past, that photo shows it's now on a different boat).
Perhaps further research is needed.
see here:
http://www.freerepublic.com/focus/chat/3644414/posts?page=1059#1059
The other Kennedy yacht is the "Manitou," which was a racing sail boat yacht without an enclosed bridge, and is the one you see with stanchion and rope/metal railings, stays for the mast, with an external ship's wheel and binnacle, the one with Kennedy at the wheel. This is the wheel of the "Manitou":
It is the Manitou which has the decking curvature and the kind of wood work that matches the photo with the bell. The "Honey Fitz" has essentially flat decking, as it has metal decking under the added wood.