The problem with the Boston arrivals is there is an 8 1/2 year gap on M277 (which is titled Passenger Lists of Vessels Arriving at Boston MA 1820-1891) The gap is from a April 1874 to 31 Dec 1882.
That is because there are no Federal records of any kind prior to 1883 (due to fire) and State Department copies were used in their place. BUT State Departments copies and abstracts only covered up to end of March 1874.
However the good news is that there ARE records for the missing years. They are not available at NARA, only at the Massachusetts State Archives
There is an index on M625 which *does* cover those "missing" years. Finding an ancestor on that index in those missing years means you have to then write to the Mass. State Archives for a copy of the passenger list page with your ancestor on it.
Search for ancestors on Ships Passenger Lists to USA