Another one bites the dust.
The part that is broken is the second one for the boat, the first one broke when the first mast broke in the Solent. It is a custom made piece, I think that one was Nylon as that is what they had as time was rushed. The reciprocal plug that is fitted to the mast was made at the same time to ensure a proper fit. I was charged £25 at the time (2005 I think). The spigot was made square and was a honeymoon fit in the plug, I chamfered the forward and trailing edges by hand to accommodate mast rake etc hence the rough look.
To repair the broken item I would remove the current fitting (2 screws on the fordward face and three from the top) and then re-fit the broeken off peice by 2 coutersunk machine screws from below. Then re-fit the step. The shear loads are small and 2x M6 screws should be up to the task............. however I can't quite remember how thick the base of fitting is.........you might not have much for the countersunk head to pull against.
The final option is to screw the broken off piece through the base into the top of the stump all from above. No need to remove anything. The top of the stump holds a lump of hardwood which allows you to screw fittings into (gooseneck etc, although the original gooseneck was a moulded in carbon affair but the hardwood was bonded in during build so that a quick fix could be applied to any broken gooseneck or mast step in between races at an event). You would need screws thin enough to fit through the broken off piece and make sure the heads fitted in the recess in the mast plug.
No reason not to be back on the water this evening

Gavin