Octane differences

[FishStretcher]

You will likely find that non ethanol fuel makes more power above 5000 rpm. It does in my car (but it it lightly turbocharged). 91 non ethanol makes more power at high rpm than 93 E10. Otherwise, power is the same. This in a car with a knock sensor. I'd suspect a EFI merc I/O or a supercharged outboard would be the most similar as they have knock sensors.

But the knock sensor retards timing to make power. Not remove it. Less high rpm advance means less negative work means more power.

It appears from the data I collected that E10 burns a lot more slowly than non ethanol. With a lot more advance and LESS power above 5000 RPM.

Anyways at cruise, differences should be minimal. But rec 90 or 91 Mogas is likely ideal for outboards if I extrapolate my data.