I just received this from Rick Henderson:
Both images are the same Shay at different times; we do not know the owner yet.
The item in question was added by the owner and is a steam powered
centrifugal pump for drafting by hose from a pond or stream. The hose, in this case about a 2½"-3" was attached to the fitting below the deck board.
Many Shay had these pumps installed by Lima if ordered, but not all.
The spade looking item above the pump is either a removable seat or the end of a broken shovel.