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.
