It's a 1959. That was the last year for dual line systems on OMCs. Plus, it was the only year they had the round appliqu? on the top of the cowling. 1960s had an arrow appliqu?.
Nice motors. I have three 10s to go through this winter - a 1955 Johnson, 1958 Evinrude and 1960 Evinrude.
1959 serial numbers were 1,743,081--1,995,465. So, anybody that said 1959 is the winner. Model number would be CD-16.
cd-16 is a 5.5