Most likely not... The amounts of water that creeps through the bolt holes and the gap between casting and pylon is minimal.
More likely is hull to deck seam, worn hull bottoms and drain plug and their housings might be the cause for the leak. Do the reversed vacuum cleaner trick to search for the leak. Search some of the old posts here on the forum.
Regarding the lead.... only a few Hobies have lead filled pylons. Chances are that yours might not be one of them. The amount of lead is not all that exiting.

Patrick