Ok I have a 1994 Merc 135. Been an awesome motor. I am second owner and the previous owner an I have only run 93 Shell gas in it. Now that you can get non-ethanol fuel (only in 87 that I have seen) which is better and why. I use the ethanol buster and stabil in all refueling. Thanks in advance

I'd say non ethanol 87....since that's probably what is recommended by the manufacturer.

The book (yea I read it) says minimum 87 Octane.

well, as understand it, running anything with a higher numerical octane number than recommended is simply wasting money. Wasting money on more expensive fuel....and potentially damaging the engine and costing even more.

The higher octane fuel may not burn as well in the motor designed for lower octane. I could be wrong....but I know I'm right on the wasting money part.

High octane burns slower, can cause issues. Run 87 as specified, 93 waste of money. If you can find ethanol free it's fine. Use a good additive, marine stabil or seafoam. Fill your tanks after each outing and that will keep them from injesting air, which is the source for the water the ethanol separates out with. The worst thing you can do is leave your tanks half full with no additive. This is the same for any piece of intermittent use equipment.

87 NON ethanol!! With Stabil360 Marine fuel stabilizer with Mercury Quickleen to keep carbon buildup from occurring.
Benefits:
1. Eliminate the possible issues caused by ethanol
2. 87 Octane burns faster and is recommended on that motor.
Ethanol= BAD. Stabil/Quickleen= GOOD

For future reference. Buying higher octane is a waste of money for YOUR outboard.. Octane is ACTUALLY a retardant. Higher octane slows the burn down. If anyone tells you it burns hotter they DONT know what they're talking about. Its the amount of Heptane in gasoline that determines heat range. All pump gas contains about the SAME amount of Heptane regardless of Octane amount. . ETHANOL isnt good for engines & ALSO wreaks havoc on fuel lines, fuel systems, fuel delivery carbs & fuel injectors due to phase separation & attraction of moisture(water).
Ethanol ALSO is an octane booster. Next time your in autoparts store, pickup a bottle of Octane Booster & read the label on it.

So the OP has a 24 year old motor that he says the previous owner and himself only run 93 Shell and everyone is screaming use ethanol free fuel. Funny thing is Shell has had ethanol in their fuel for the past 15 years or so. Why switch now....
As long as the motor is used regularly and the fuel doesn't sit for months at a time it's a non issue. Worst case is the fuel lines should be replaced because back then they used a different material that didn't always react well to ethanol.

Your motor will feel stronger and run better on 87 real gas vs 93 corn likker.

He's ALSO PAYING more money per fuel up for NO benefit.

I was wondering the same thing. I'm getting a 1999 Mercury that my dad swears the recommendation is for 93 octane and thats all he ever runs in it. He doesn't even think about ethanol or non ethanol. I was thinking 87 non ethanol.

Unless its a Promax or 2.5EFI race motor then the recommend octane is 87

150 Optimax

Have run 87 octane with ethanol since day one in my 1989 ProV150. Have always used Stabil Marine fuel treatment. Boat's gas tank lines and engine's fuel lines should be checked to ensure they're ethanol resistant. No fuel problems in 29 yrs. Higher octane gas IMO is waste of money in engines designed to run 87.

This is the OP guy....I just ran about 10 gallons of 87 non-ethanal gas with Stabil in it on Choke Canyon yesterday....well engine ran like a champ but the fish did not cooperate. I am sticking to the 87 non ethanol fuel from here on. Honestly it is more expensive than the traditional 87 but I figure in the long run it will keep that older fuel system from deteriorating.

Guys...thanks for all the advise!!

87 without