Can anyone tell me the ratio of fuel mixture and what type of spark plug l should use for a 1964 75hp Evinrude motor with the model # of 75483-d?If it matters, this is the electric shift motor.TIA

Two stroke engines back then mostly used a 20:1 mix, but with the newer oil, you can do a 50:1 mix with no issues nowdays in the older engines.

You can go to almost any ''Good'' parts store and they have the plug books that will tell you what plug to buy for that model and year.