My SM for that series of engines but in the 90-125 HP category states to expect problems below 120. You have a smaller engine which may have a different crankcase design allowing for a lower limit. Even if you don't you aren't that far down so If I expected problems they would be minimal....like you used to run xyz MPH at abc RPM and you are down a bit from where you were.
The manual also states 87 octane is the MINIMUM for these engines. Moving up to premium should get you better performance....does for me and my compressions are in the 130 area.
