Re: 35hp Elgin.
Elgin was a house brand name for Sears outboards. According to some sources, they were made for Sears by West Bend from 1946 through 1959. After that, the motors were supposedly made by McCulloch. That said, there is apparently a 1965 35hp model that carries the Elgin name.
I would say that your motor is most likely a 1958 or 1959 model Elgin, but it could be a 1965 too. To confirm that the motor is an Elgin, look for a model number that begins in "571."