hey all,
new to the forum, thanks for having me.

ive got several OMC motors, but the ones in question at the moment are a 62′ Johnson 28 hp, a 63 Evinrude speditwin 28hp and a 66′ evinrude skitwin 33 hp. i understand the old bushed crank shaft motors required a very thick oil mixture to prolong their life. my 57′ 3hp sea horse requires 16:1 mixture it is my understanding that the pre 65′ larger motors, like my 28s had roller bearings, and there were very little changes between engine design from 64-65. so my question is why the change in oil mixture? is it that OMC was reacting to pressure because Mercs were already using 50:1? were they experimenting with it pre 65′ and finally were satisfied it would work? was it the advent of better oil?
i may try some biodegradable 2 stroke in my older models but i wondered what the thoughts were in using 50:1 in the earlier 60s motors?
Seth