Navy PBY Catalina Squadron of WWII
Photos: Cliff Dohrmann Collection

Engine change: 11-P-4

I'm guessing from the Neutrality dot in the national insignia:
this photo was taken before 1941-Dec-07, or
11-P-4 survived 1941-Dec-07, or
11-P-4 may have had a different side number (i.e. was from another squadron) before 1941-Dec-07.

(Photo courtesy of Cliff Dohrmann)