I just bought a drift boat with an older Evinrude Fisherman, long shaft. Serial # 5302HE07484-. In one site, it looked like a 1963, but would like to confirm. FuelOil/ mix on other posts were 401/ or 501/, is this right?
That's a '63. In 1963 all OMC motors were 24:1, in 1964 they all went 50:1 together. So the correct answer is 24:1 with 87 octane gas and TC-W3 rated outboard oil.
For a little more information, there are no known internal differences between the '63 and '64 model. But those who know these machines recommend you run the '64 and later ones more like 40:1 for maximum longetevity and protection since they really weren't cut out for 50:1 service. Personally, I think it's best to keep these fellows greasy and stick with 24:1.
Check out the oil mix FAQ in the FAQ forum for more information.