87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

[kknickelson]

I've been reading way to much on the octane subject. Some threads talk about octane and some talk about ethanol. In Mn I have the option of non oxygenated 91 octane or 87 octane with ethanol. The question is ... what is worse for my engine, ethanol or the higher octane?

Did we even have ethanol in 1994? Manual says minimum 87 octane.

Just an fyi ... I run seafoam in every tankful.

Please advise.
Thanks

 

[cbcmarine]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

I've been reading way to much on the octane subject. Some threads talk about octane and some talk about ethanol. In Mn I have the option of non oxygenated 91 octane or 87 octane with ethanol. The question is ... what is worse for my engine, ethanol or the higher octane?

Did we even have ethanol in 1994? Manual says minimum 87 octane.

Just an fyi ... I run seafoam in every tankful.

Please advise.
Thanks

Ethanol is a marine killer, always run the non ethanol gas. I have run a marina and have seen nothing but problems with ethanol. It is fine as long as you burn it up quick but leaving this fuel in your tank for any length of time causes nothing but problems

 

[SingleShot]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

My 03 merc manual states not to use any gas with ethanol in it. I run the 91 octane with No ethanol. It can be pricy, but cheaper in the end. My neighbor has been having lots of engine issues because of running the ethanol blend. It's taken a couple of seasons and now he has been regreting it.

JK

 

[Fishin Magician]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

My 03 merc manual states not to use any gas with ethanol in it. I run the 91 octane with No ethanol. It can be pricy, but cheaper in the end. My neighbor has been having lots of engine issues because of running the ethanol blend. It's taken a couple of seasons and now he has been regreting it.

JK

hey JK...
where do you buy gas with NO ethanol in it......it is 10% here in upstate NY.....
can't seem to locate straight gas around here anymore.....
on my little merc OB 's ....I just pull the gas line and run the motor out of gas after each use....even while still in water for season....
same with my motorcycle....after each use..I just cut fuel supply and with long screw driver I reach in and drain the bowls to get all gas out....ethanol is not our friend....

FM

 

[wired247]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

My 260 HP 2.5 liter manual says 92 octane and up to to 10% ethanol. I wouldnt store the stuff over the winter but for high use summer gas ethanol is fine

 

[Silvertip]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

Dude -- you are in Minnesota as I am. Run either one. Ethanol is not the demon fuel the uninformed tend to make it. If it was so terrible the ditches would be littered with discarded outboards. You run SeaFoam so the fuel system is protected. I will assume you've been running regular fuel (E10) and have not had any issues. If you want to eliminate degradation of rubber parts, replace the fuel system components with ethanol tolerant parts and go boating. Unless you tune the engine for 91 octane you will get no benefit and possibly a loss of performance from it. 91 octane does not provide more power. It allows an engine to run with more spark advance. Your engine is designed to run on 87 octane (regular)

 

[kknickelson]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

I'm rebuilding carbs and some other maintenance. Looking at my shop manual it states to use minimum 87 octane without ethanol. Just thought I ask the question. I've also been looking at some of the synthetic oils too. Way to much info out here on gas and oil. Trying to look at this info and make an educated decision.

After all.... if it's on the internet .... it must be true... lol

 

[Laddies]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

Regardless of what anyone tells you about ethanol and how good it is, alcohol and petroleum bases oil will not mix! So what lubes the engine when the alcohol goes through it as the ethanol will not mix with the gasoline either.

 

[wired247]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

Ethanol mixes just fine with gasoline. The problem is that ethanol mixes even better with water. Pulls water out of the air ethanol does. Then that water saturates the ethanol and drops out to slink around that the bottom of your gas tank until your pickup sucks it up.

I'll use it in the summer when I go through 10+ gallons a week from my 12 gallon tank . I won't use it in the winter or put my boat up for any period with E-10.

 

[Laddies]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

Ethanol, is nothing but pure grain alcohol, which will not mix with gasoline in less agitated, even then will separate under the right conditions (called phased separation) at that point nothing will return it to it former self and there are no additives that will help either. Even if the two were entirely compatible the problem lays with the inability to mix with oil in two cycle engine and that alcohol causes lean operating conditions in a fixed jet carburetor on two cycle engine. Some enginee are approved for E10 but if the engine has a major failure, hang on for warranty and hope the fuel does not test more than 10% which is common with some E10 fuels as you may not receive the warrenty you expect.

 

[wired247]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

Ethanol mixes readily with gasoline . It does not phase separate until it gets water in the blend.

 

[Laddies]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

This is hardly worth the effort but take gasoline in a beaker or glass jar and mix in 10% alcohol and 2% TCW rated oil, shake them up and then let them sit for a few days. Then tell me they stayed togather or you could just read anything on ethanol, that is not published by the energy companys or the federal goverment. While on the subject of ethanol, the corn surplus has been used up so now the corn that normal feeds this nation and many more is gone and future ethanol comes out of the food supply, how smart is that?

 

[JB]

Re: 87 octane with ethanol or 91 octane without... 1994 Merc 75hp 2 stroke

Right. I think I have it now. Ethanol does mix with gasoline but it doesn't mix with gasoline. What we have been using for 20 and more years destroyed our engines that still run fine.

Good grief, people. There is more misinformation in this thread than useful information. How do we tell the difference??

At least keep it non-political and non-controversial.. . .um, never mind. Closed