Re: Regular(87) or Premium(93) gas for 1998 Force Mecury 75 2 stroke
Justin: A serious question deserves a serious answer. Octane is one of a number of straight chain hydrocarbons starting with methane at one carbon and four hydrogen atoms per molecule going up to ethane, two carbons and six hydrogen atoms. Replace one hyrogen with a hyroxy molecule (OH) and you get the alcohol ethanol. These long chain hydrocarbons can go up into hundreds of carbon atoms and gasoline is a mixture of both short and long chain to give a specific octane number.
A long time ago (and in a universe far, far away LOL) The Society of Automotive Engineers (SAE) set octane (8 carbon and 18 hydrogen atoms, clear aromatic liquid with a moderate flash point) as the base from which all other mixtures of hydrocarbons (gasoline) would be graded.
Pure octane was arbitrarily set at a 100 knock (detonation, pinging) resistance on a standard test engine. All other fuels are compared to the knock resistance of octane and can be higher or lower. All pump fuel sold in the US today (as far as I know) is less than 100 octane rating however, during the glory days of muscle cars, Sunoco did sell either 102 or 105 octane rated fuel. (Race fuel of NASCAR--can you spell marketing hype?) Muscle cars with 13 to 1 and higher compression ratios did require this high level.
The higher the octane of a gasoline, the SLOWER it burns (usually). Greater power is developed by increasing compression ratio, changing valve timing, and advancing ignition timing. Indeed years ago, when tourists took automobiles into Mexico from the US for an extended stay, the lower octane fuel sold there required timing to be retarded slightly. AND, if you remember, in the late 70s and early 80s, Chrysler advised changing timing on their outboards from 32 BTDC to 30 BTDC because of lower quality marina fuel.
So, in summary, higher octane fuels do not burn any cleaner, do not burn any smoother, and of themselves do not generate any more power. Their only advantage is in a engine set up to deliver maximum power and requiring them because of the factors mentioned above. ANY other use, especially in an outboard with only 8 or 9 to 1 compression ratio, is because of "faith" or "Religion" and a waste of money.
