Re: what is the oil ratio 59 evinrude 35hp
Mark, Although I agree with your line of reasoning on 4 cycle motors, I do not think it applies to 2 cycle motors. When 2 cycle motors were using 16::1 and 24::1 gas oil ratios, they also had sleeve-type bearings. When 2-cycle motors went to all needle, rollar and ball bearings, the 50::1 gas oil ratio was acceptable for lubrication. In the case of the '59 Big Twin, I believe it is all needle, rollar and ball bearing consruction. if so, it can use 50::1 mix. If does have some sleeve bearings, than it should use the 24::1 mix. Today's TCW-III oil is much better than the straight weight oil of 1959, in terms of mixing, carbon buildup, coking and other factors, but it is not "superior enough" in lubrication to protect sleeve bearings, when mixed at 50::1.
BTW - Automotive oils need to be drained and changed due to acid buildup and and additive package depletion, rather than viscosity issues. This is why modern oils (better additive packages) outperform older oils, and do not need to be changed so much. However, if you look at the SAE grading of oils, the designation changes nearly every year, which indicates that the oil is improving nearly every year. Newer cars can take advantage of these improvements, but as you have seen in the maintenance schedules, oil change intervals do not rise each year. This obviously mean that the improvment in oil performance between years is not too great.