What is the correct mixture for my 18 horse 1957 evinrude fastwin model 15020. According to evinrude web site, pre 1958 is 20:1, 1959-1963 is 24:1, and 1964 and up is 50:1. my Dad ( whom I inherited it from) used a 32:1 and ran it for 30 years with no problems. But with the newer oils out there I was just wondering?
