It is surprising that he was drowned in August 1846, and the death not registered until June ¼ 1847. In those days an inquest was held either the same day as the event, or the day afterwards. One reason could be that his body was not recovered until 1847.
As an example In The Bristol Mercury of Saturday, January 30, 1847, there is a report of the inquest of a John Cleuny who drowned on the previous Friday afternoon, by falling from his ship, and the inquest was held on the body on the Friday evening.
As I understand it the general requirement was that an inquest was held immediately upon the notice to the coroner of the death or discovery of the dead body. Apparently statutes required that the coroner and jury must have a view of the body together except in cases where the body could not be found or was too decomposed for view. The purpose of this inspection was to ascertain from the appearance of the body how the death was caused.
Stan