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The oil got better and has to continued to improve.
Factory ratings changed over 50 years ago. Tubs
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Thanks Tubs, I have that 1971 Service Notice. I will go forth with trepidation and use 24:1 for the early 60s and 40:1 for the 1967.
I also note that they recommend “Leaded” gas for all.
Read the asterisk that applies to your model
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I can learn new things. I’ll shake off that 16:1 urge for the mid to late fifties. But after so much work and so much help from the forum to get my 55 Evinrude 5.5 back to life…..well, I worry.
OK, this perpetual discussion continues.
For sure, outboard oils have improved over the years, no doubt. The question is has the oil quality improved enough to lube those plain rod bearings adequately at a lower ratio? Perhaps on the 3hps.
But, on the 5.5s/7.5s, I don’t think so. I would always stick with the original 16:1 recommendation. The beauty of these old engines is that when in proper tune, they hardly smoke, even at 16:1. That rod set up is definitely the weak link to otherwise bullet proof engines.
What about the argument that “OMC even recommended lighter ratios on these engines using the newer oils”. I’m thinking most of those recommendations came from short time OMC staff/engineering/sales folks that had little or no experience with the 5.5/7.5 models. Keep in mind that it was probably the same type of OMC staff the promoted the 100:1 mix in the 80s, and we all know how that went.
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Back in “The Day”, I asked an Evinrude Engineer, face-to-face, about what changed to make older motors ok with 50-1. He said “sometimes, they just found out that their motors didn’t need as much oil as they thought they did”.
But is today’s oil better? Hey, back then you could go to your local gas station and buy used drain oil in glass bottles with a metal pour spout. It was sold as re-refined oil or something like that.
1970’s era was the start of the outboard horsepower race. They were making 140hp motors in similar size and weight as the old Fat-Fifty. Terrible timing, leaded gas was also being phased out. And high performance/high compression motors were busting pistons from pre-ignition and detonation caused by low octane gas. The lead was needed for the octane rating in those cases.
Cars too, I owned two high compression cars, a 110hp Corvair and a Pontiac Bonneville. The lead was needed for the octane. I had the timing set so far back in the Corvair that it couldn’t get out of its own tracks. But it still pinged even while going downhill. Both cars were sold because I couldn’t get gas for them.
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