The 277181 was the original correct impeller but I know this was superseded to part #434424 which has an ID of 0.44″. Don’t know if that is any different than the previous 277181. I upgraded my CD-11 to the new kit #763758 with a different (plastic) impeller housing and a taller impeller but even that impeller has an ID of 0.44″. Not sure why yours doesn’t fit.
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."