Re: Oil mixture for older evinrude
That is the first time I have seen the 20:1 spec for '58 and prior. For 45 years I have gone by the tenth edition of the factory Johnson Service Manual which said to use 24:1 in all OMC made engines of 1963 and earlier, and 50:1 (48:1) in 1964 and all later engines.
More recently I have seen the 20:1 spec for 1950 and earlier.
Heck, the fact is that they can't make up their minds about pre 1964 engines and change the spec every few years with no explanation why, except when they withdrew the 100:1 spec for mid-80s engines because engines were rusting internally in storage.
I would use 24:1 on both your engines. 1 quart of TC-W3 oil to 6 gallons regular unleaded. The 16:1 ratio was for SAE 30 motor oil, not TC-W3.
