Was the boat out of water for a long period??? If the packing (inside the fitting) is made out of hemp or a similar material then the answer is yes... Hemp dries out & shrinks and will leak until its been wet for a while and then it expands & fills in the space. Its used often in wood boat building as caulk between planks, packing material for through hull fittings, etc...
Modern materials & better engineering have replaced it, but that may be why your shaft packing was leaking and has since stopped.