i have twin 500 hps carb motors with msd boxes and worked carbs, i run 87 octain would there be any gain running 89 as i do get alot of black on transome.

If you run good and safe on 87, you'll get more soot with 89. It won't burm as hot or complete.

The only benefit of running 89, is your wallet will be lighter to carry around.


Darrell.