If you use aluminum for masthead cranes, you undoubtedly glued it in with epoxy at the top of the mast. This is ok until you want to remove it. You could saw off the crane, but you will loose some mast, and you don't want to do that. You could try to pull it out (good luck) or you could buy a new mast. There is a better way according to Charles Ellis and Craig Mackey, melt it out.

To do this, get a hand held propane torch and a pair of pliers. The goal is to heat the aluminum masthead crane just enough to melt the harden epoxy glue and quickly pull out the crane. Start, heat the aluminum masthead crane at the ends. Don't heat too close to the mast or you will over heat the aluminum and damage the carbon fiber mast tube. Just heat the aluminum just enough and after a short time start pulling and/or turning with the pliers.

When the aluminum gets hot enough and starts to melt the epoxy, the crane come out. Don't worry about the crane, you can't use it because the metal is now soft and is bent. Once it is out, quickly blow on the mast to cool it off. Now you put on a new masthead crane that will do the job better.