Is there 2 more holes at the same height along the side of the motor? If so, then that probably is a freeze plug. Freeze plugs can be shaped like a dish or like a cup. Since that hole has no ledge in there to stop the plug from going right into the water jacket in the block, it should have a cup shaped plug. Auto parts should have them.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.