Re: Oil/Gas Mixture 1980 Mercury outboard 90HP
Thanks! I was told to use premium gas though. What's your take on that?
Here's a simple rule of thumb if the engine is jetted for sea level operation. 1. 0-2500 feet 87 octane
2. 2500-5000 feet 89 octane
3. above 5000 feet run 89 and drop 2" of prop pitch.
This is by no means a perfect measure but it works with a fair degree of success in most cases.
Just remember, higher octane means a longer fuel burn and burning the fuel further through the stroke will produce more power in the correct conditions.
