Had similar issue with my H16 mast head.
Carefully used a small chisel / screwdriver and a mallet to slowly pry it out, changing position around the edge as I went, light'ish but sharp taps.
Make sure you have banged through all the rivets, five of them on the H16 not entirely sure of the number on the H14.
Just go easy as the last thing you want to do is crack the casting, though it is quiet tough.
If as MMiller mentioned it is stuck with 3M 5200 adhesive the following may help http://www.marineformula.com/faq.html