I have a spreadsheet showing 4319 was used a number of years. The serial indicates the year:
Evinrude,1939,1939/45,4319,Lightfour-HD-Long Shaft,up to 03000,9.70
Evinrude,1940,1939/45,4319,Lightfour-HD-Long Shaft,03001-04000,9.70
Evinrude,1941,1939/45,4319,Lightfour-HD-Long Shaft,04001-05000,9.70
Evinrude,1945,1939/45,4319,Lightfour-HD-Long Shaft,”05001-90,000″,9.70
Evinrude,1941,1939/45,4319,Lightfour-HD-Long Shaft,”90,001-91,000″,9.70
Evinrude,1942,1939/45,4319,Lightfour-HD-Long Shaft,”91,001 and up”,9.70
Which looks like the same info as in “The Old Outboard Book”
http://www.omc-boats.org
http://www.aerocraft-boats.org