Suggested Gasoline To Use?

[LSU Fan]

I have a 2013 Mercury 175 ProXS outboard.   I haven't used Ethanol-free gas in the past in this motor but have been adding the prescribed amounts of Quicksilver Quickleen & Quickare fuel additives since day one of having this motor.  I have only used to this day BP/Amoco 87 octane.  Also when fueling up for a day on the lake usually only add 10 gallons of 87 oct. unless planning to run more on the water than initially planned.  That said I sure would like to receive a bit of feedback on whether or not to burn ethanol-free gas in my Mercury.  Presently BP only has ethanol-free gas in their Silver Grade of gas and I only have seen 89 octane.     

[J._Bricker]

@LSU Fan I’d just keep using the BP/Amoco 87. It was my experience with my old ’04 Optimax when using higher octane fuels the longer burn time damaged the air compressors. Sticking with the 87 octane and Mercury fuel additives should help keep your Opti trouble free. California’s gasoline is 10% ethanol by the way. Good fishing.

 

*My old 225 Opti had 923 hours on the original powerhead and running strong when I sold it for a new boat with a ProXS.

[Jig Man]

I ran 87 in my Opti for 14 years.  I used Quickleen.  My boat was an 01 and I did have to get the fuel lines replaced as my tech said that ethanol would damage them and clog my injectors.

[Functional]

Going to show my rear here but I never used ethanol free gas in my 2013 with merc 60 and no additives during the summer months. When winter hits I'll fill it up to the absolute max and put in additives and if I use it I keep it topped off but thats it. Still running like the day I bought it. 

 

Only thing that gets ethanol free gas is weed eaters, lawn mower and leaf blower because they sit after the fall. 

[K1500]

I use only ethanol free and use stabilizer with every fill up, but it’s easily available at most gas stations and it’s all the marinas carry. I figure it’s pretty cheap insurance, especially after having the FI system in a motorcycle gum up over winter with E10 ethanol fuel. As long as you are treating it and running fuel through it on a regular basis, it probably doesn’t much matter what you use. 

[gimruis]

56 minutes ago, Functional said:

Only thing that gets ethanol free gas is weed eaters, lawn mower and leaf blower because they sit after the fall. 

 

 

That's the key here.  If you use the engine all year round on a regular basis, there's no need for ethanol free gasoline.

 

For us northerners, our outboards are only seasonally used.  Same with our snow blowers and lawn mowers.  Its when you use an engine with ethanol and then it sits around for months on end is when problems can occur, usually related to the carburetor.

 

The OP is in North Carolina, so I imagine he's able to use the boat almost all year round.  Normal gas is fine.

[Functional]

@gimruis when I lived in middle NY that was the deal. Used it in the summer with normal gas and towards the end of the season switched to ethanol free in prep for the winter. 

 

Currently live in NC and the above is my new practice. Just leave the least amount of air gap for condensation to build up and an additive in NC winter if you arent going out regularly.

[Bankc]

Run whatever the motor was designed for.  Nothing more.  Nothing less.  

 

The only time I buy ethanol free gas anymore is for my 2-stroke engines that aren't designed for it.  The only time I buy high octane gas is for my wife's Miata which has a high compression engine.  And the only time in my life that I've ever had engine problems related to fuel was when I bought old gas at an old gas station, which I knew was a mistake, but I didn't have much of a choice at that time.  

[MN Fisher]

10 minutes ago, Bankc said:

Run whatever the motor was designed for.  Nothing more.  Nothing less. 

Bears repeating - use what's recommended by the motor manufacturer.

 

My old 25hp Evinrude 2-stroke gets nothing but ethanol free.

[DaubsNU1]

Agree with @gimruis, if gasoline engine is used regularly, run ethanol blend. And also agree with @MN Fisher, follow manufacturers guidelines.

 

When it comes to small engines (weed eater, Lawn Boy, snow blower, leaf blower, generator, power washer, chain-saw) and ATV's, it is, and has always been ethanol-free gasoline. Even with two-stroke engines. My weed eater sat from November in to April in un-heated shop here in Nebraska. While not as cold as Minnesota, still darn cold.

 

I never even drained fuel from the tank...and it fired right up this spring, no issues what so ever.

 

I always ran ethanol-free fuel in my old 1960 Mercury 20hp 2-stroke. I did run the engine dry after every trip (just pull the fuel line and let her run out). Again, never an issues. Fired right up every spring. The new Mercury 90hp gets ethanol free fuel, and stabilizer in the winter when stored in the shop.

 

In my daily-driver, 2005 Accord, it gets the cheapest gasoline available...I'm driving 65 miles around trip to work daily. 

[Tennessee Boy]

I would not exceed the recommended octane.   You might want to check this website to see if there is ethanol free 87 octane in your area.

 

https://www.pure-gas.org

[Woody B]

 

Keep doing what you've been doing.  Don't try to fix something that isn't broken.   

 

This goes for anyone who isn't having problems, regardless of what fuel they're using.  

[Susky River Rat]

Yeah, I’m big on the used what has always worked for you. I run ethanol free with marine 360. That’s just me never had issues. If you aren’t having issues don’t change it. 

[Skunkmaster-k]

Yes 

[airshot]

My 1992 Merchant OB calls for unleaded 87 octane with up to 10% ethenol and to add stabilizer for long term storage over 90 days.  The motor has received that since new, no issues, motor runs and looks like new !!  Chainsaws, trimmer, rototiller, and all gas powered toys use  E 10 fuel with a shot of stabilizer like recommended and never an issue since E fuels came onto the market.  Watch where you buy your fuel !!  Most issues are caused by buying poor fuel to begin with !!

[Way2slow]

It's your motor, run what makes you feel good about what you are using.

I have at least a nickels worth of experience with motors, and I personally don't buy ethanol free; todays motors are designed to run up to 10% ethanol. 10% ethanol became pretty dominate back in the late 80s to where you had a hard time finding non ethanol.  Back then the motor manufacturers didn't have all the bugs work out the ethanol caused with hoses, gaskets etc.  From the mid 90's on, they pretty much knew what they were doing, and I've never given it a second thought about pulling up to an ethanol pump.   However, like everything else on the internet, one person can have a problem and a million people will make it sound like they had it.  A million people can never have a problem and you hear nothing about it.

 

I only have two pet peeves about the gasoline I use.  The main one is it has to be a Teir 1 brand, none of that discount junk.  I don't even run that stuff in my lawn mower.  

The second is I only buy from high volume stations, that reduces the chances of getting bad gas.  

I also try to buy only what I think I'm going to burn with a little extra, that way I don't have to worry about having a lot of gas going bad in the tank if I don't go for a few weeks.  I only use SeaFoam in the gas when I know it's going to be sitting more than a month.   About every 50 hours I will add 1-1/2 oz per gallon, just to help clean the engine.  It the gas you are buying is a good Tier 1, all those extra additives are just money dumped into the lake. 

Old/bad gas damages a hellavalot more motors than that little ethanol, it just helps make the gas go bad quicker.  Today's gasoline goes bad very quickly.  In a boat sitting outside in the sun, a month is the max I will leave gas in a tank, and stored inside, two, no more than three months is the max I will let gas sit in a tank and even then I want SeaFoam in it.

[TnRiver46]

Here is an actual photo of my boat, it’s a 4 stroke. It’s almost like they are trying to tell me something 

[WRB]

I always used premium 91 octane gasoline in my Mercury OB’s for decades without any issue's. 

When 10% ethanol additives came the pumps had to add labels that said this fuel may contain ethanol but corn ethanol was rare up until around 2000.

California didn’t allow the sale of unleaded gasoline for vehicles however the majority of gasoline sold was 87 octane and ethanol supply was more prevalent in lower octane gasoline.

If your engine is used for racing 101 plus leaded gasoline ( Aviation ) is what I ran back in the day

To answer the question use fresh 91 octane.

Tom

[slonezp]

Been my experience to use 87 if the manufacture recommends it. If there is no ethanol added, I don't see why you can't go higher than 87. If you are filling with ethanol, stick with the octane the manufacturer recommends. 

[MickD]

What you are getting here is a lot of opinion based on varying experiences, not scientifically proven advice.  So here's mine:  I don't think there is a significant difference in performance or durability of 87 and 89 octane fuel IF the engine does not knock on 87.  So I believe the octane argument is moot since your engine works fine on 87.  I also believe that since ethanol is basically and unarguably a negative for fuel lines AND the engines themselves (I have had two devices totaled by ethanol according to the shop) I use and recommend ethanol-free fuel whenever it's available.  I would keep using the additives since they have been successful for so long even with ethanol fuel.  There is no down side except cost to 89 octane ethanol-free fuel.

[gimruis]

10 hours ago, slonezp said:

If there is no ethanol added, I don't see why you can't go higher than 87.

 

Our ethanol free fuel here is only in premium grade (91 octane), so that's what I buy for my seasonal engines.  If it was offered in a lower octane, I'd buy that.  I just want the fuel without any ethanol for my outboard, snow blower, and lawn mower.

[Will Ketchum]

If you have a history of problem free operation with what youv'e been using, stick with it.

[Bankc]

2 hours ago, MickD said:

What you are getting here is a lot of opinion based on varying experiences, not scientifically proven advice.  So here's mine:  I don't think there is a significant difference in performance or durability of 87 and 89 octane fuel IF the engine does not knock on 87.  So I believe the octane argument is moot since your engine works fine on 87.  I also believe that since ethanol is basically and unarguably a negative for fuel lines AND the engines themselves (I have had two devices totaled by ethanol according to the shop) I use and recommend ethanol-free fuel whenever it's available.  I would keep using the additives since they have been successful for so long even with ethanol fuel.  There is no down side except cost to 89 octane ethanol-free fuel.

I'd find a different shop if they told you two engines were totaled due to ethanol fuel (assuming you didn't use something like e-85 fuel in them).  They clearly don't know what they're talking about, and just blaming a boogey man rather than admitting they're out of their league.  Now ethanol can damage an engine.  I'm not arguing against that.  But it certainly won't total one.

 

Ethanol's only issues are it absorbs moisture from the air and has an alcohol component.  The added moisture can cause unprotected steel or iron components to rust, and the alcohol can damage some types of rubber hoses and seals.  Most modern engines were designed for use with ethanol and so won't rust or break down when exposed to water or alcohol.  Even on an old engine not designed for ethanol, the engine itself should remain unharmed by ethanol exposure, especially if it has a fuel filter.  Worst case scenario is usually the carburetor gets clogged with gunk being passed from the fuel lines and tank.  Then you just rebuild the carburetor to get the engine going again.  A hassle and a cost you don't want to pay, but not enough to total an engine.  They generally don't recommend ethanol gas in 2-stroke engines because the ethanol will accelerate the separation of the oil from the gas in the blended fuel, reducing the engine's lubrication.   Especially if the fuel sits for a long time and isn't mixed up, like what happens with a lot of 2 stroke engines.  Though you can still run old 2 stroke engines with ethanol added gas just fine, so long as you don't let the gas sit for long periods of time, unused.  

 

As for the octane thing, higher octane gas doesn't burn as fast and thus reduces power from the engine.  It's actually the exact opposite of what most people think.  The advantage of high octane gasoline is that when you compress a fluid, you raise the temperature and pressure of that fluid.  And if you have a high compression engine that raises the pressure before firing, the cylinder can fire prematurely due to the compression pushing the gasoline above its ignition point before the spark plug fires.  That's what engine knocking is.  It's the gas in your cylinder exploding before it's supposed to, throwing the engine out of timing.  So you need high octane gas for high compression engines so the gas doesn't accidentally fire before the spark plug sets it off.  Running too high of an octane gasoline in an engine that wasn't designed for it usually won't harm your engine, but it will reduce power (slightly) and waste money.  

[Way2slow]

Wow, Bankc actually knows his stuff about these things.  As I mentioned, if you are using Teir 1 gasoline all this voodoo magic stuff you put in the tank everytime you buy gas is wasted money, but if you feel it's needed, and you feel better about using it, go for it.  An OEM stock motor designed to burn 87 octane should only be run on 87 octane.  As you increase octane, the burn time increase, (it burns slower) which as mentioned reduces performance and increases carbon build up (which happens to be the number one killer of two stroke engines) because it reduces combustion temperature.  I say number one, it's probably a toss-up between carbon buildup and bad gas.  If you have modified your engine so the compression is over 130 psi, then you want to look at increasing the octane and maybe the timing some, but otherwise, don't think you are doing your engine a favor by running higher octane in 87 octane engines.  

Run fresh, Tier 1 gasoline recommended by the manufacture and your engine will be happy.  If that don't make you happy, then run what does.

 

A little background on my experience with two strokes and outboards. I built my first two stroke motor about 1960 on an old lawn mower.  In 62 to 65 I was racing and modifying McCulloch Mac-8 and Mac-10 go cart engines.  In 67 to 73 I was racing an modifying outboard.  I got out of outboard racing but still built and modified engines for others.  In the late 90's I got into mostly just modifying OMC 3.0 200/225 engines.  My thing was taking those engines and getting 300+hp and almost 300 lbs of torque so they would launch a heavy bass boat like it was shot out of a cannon and run faster than most people had the nerve to drive one.  

I don't know much about four stroke outboards, because I got out of them about the time, they were getting popular but don't have a clue how many automobile engines I have built and modified for racing. 

A million hours using die grinders in outboard motors and automotive cylinder heads pretty much destroyed my hands is the reason I'm not messing with them much now.  

[Deephaven]

Ethanol free is the most important.  It doesn't kill engines per se, but can be devastating.  Learned that 15 years ago or so.  Had an identical snowmobile with my buddy.  I maintained both.  Every year I pulled the carbs and cleaned them.  He ran ethanol and I didn't.  The first year I did his I ****.  So much corrosion and build up a cleaning was necessary.  Mine it was more just for preventative.  His was completely disgusting with less than 100gal gone through it.  I had zero faith his jets were clean before the cleaning and if you lean down a two stroke too far ...boom.