Which gas for outboard ?

[dillrodd]

I recently purchased a 2000 60 merc. 2 stroke. Which gas is the best to run in it.

[Northlander]

Premium.

[BobT]

Check the motor's recommendation. There should be a nameplate on the outboard and you'll find a recommended minimum octane rating. Mine recommends 87 and others may recommend something higher.

[Phred52]

Premium NON-OXY. And then Amsoil. The 'recommended' is usually the minimum octane required. Premium/ non-oxy will have a longer 'tank life' and burn cleaner in the motor.

[delcecchi]

I prefer premium non-oxygenated. If nothing else it holds up better. It can be hard to find, depending on where you are. It is sold for "off road, boat, collector car".

Up north it is at all the stations. Around Rochester it is scarce. A couple of places have it though.

[marine_man]

Non Oxy will hold up longer / better. But, if it were me, I'd run whatever you choose, and run a fuel stabilizer along with it unless you're planning on burning through the gas in less than a couple of weeks. In my opinion it's cheap insurance.

marine_man

[BobT]

The 'recommended' is usually the minimum octane required. Premium/ non-oxy will have a longer 'tank life' and burn cleaner in the motor.

[Bassinbob84]

Premium with stabill and amsoil

[SkunkedAgain]

There are lots of people that give you their unequivocal statements about what is right, but it's tough to truly know who is correct and who is just making strong statements that sound good but are based on personal opinions. Since Minnesota is unique with its oxygenated fuel blends, I think it's a tough question to answer.

My new motor states that I should only run non-oxygenated gas. I've read some of the statements, such as the one Bob T provided, that say to run the non-oxy gas with anything older that was not originally intended to run on the oxygenated fuels that we all use today.

Here's my opinion statement: Unless the manufacturer of your boat motor has a stated opinion about fuels, go with the non-oxy (or 87 with a stabilizer) especially if the fuel will sit for weeks or months. Just because the motor tab says to use 87 octane, that doesn't mean much because a 2000 motor was built before Minnesota switched to oxygenated gasoline. Maybe Mercury has a statement on their HSOforum for owners of older motors. That's something that I would check out.

[SkunkedAgain]

From the Mercury HSOforum FAQ:

What octane rating should the gasoline that I use in my motor have?

United States and Canada

Use a major brand of automotive unleaded gasoline with a minimum-posted octane rating of 87. Leaded gasoline is not recommended. Performance Products will have different requirements, consult your Operation, Maintenance and Warranty Manual. Use the Bookshelf link on the Mercury Dockstore page if you need to place an order for a replacement manual.

What can be done to maintain fuel quality during periods of storage?

Mercury Marine recommends the use of a fuel stabilizer to prevent fresh fuel from undergoing degradation and oxidation during fuel storage. Mercury offers Marine Fuel System Treatment and Stabilizer both under the Mercury Precision Parts or Quicksilver brands. Additional benefits of the product includes: easier engine starting after periods of storage, elimination of the necessity to drain and dispose of fuel, prevention of the formation of deposits that could clog filters and tiny passages in the fuel system; and elimination of corrosion and rust throughout the fuel system. It absorbs water and prevents fuel line freeze-ups.

I would still want to know if Mercury is considering the non-oxy versus oxygenated fuel question in these statements. It would be nice if that acknowledged it somewhere. The next step might be for you to call. Make sure that whomever you talk with actually understands the fuel issue, and isn't just reciting back the company policy off of the HSOforum.

[SkunkedAgain]

Okay, I should have looked a little harder. Mercury has addressed the issue on their HSOforum. This is a great overview of the oxygenated/ethanol issue so I'd recommend reading the entire piece. I will also naively assume that what Mercury has said here is probably universal to all boat motors, as I can't imagine that their parts & technology over the past 60 years were that much different than Johnson, Evinrude, Honda, etc. However, I have bolded a few points worth noting:

Outboard Frequently Asked Questions:

Ethanol

Mercury Marine remains very active in developing a thorough understanding of important issues and environments in which our products must operate. Mercury's engineers work constantly to expand our understanding of fuel technologies and their interactions with all Mercury products to ensure they perform properly and reliably. Mercury personnel work in concert with industry groups, such as the National Marine Manufacturers Association (NMMA), to offer input into the overall processes by which many decisions are made regarding fuel regulations and energy policies so future problems are minimized and future developments are beneficial to those who utilize our products.

Included below is a list of questions and answers that address typical concerns of consumers.

Please feel free to contact any authorized Mercury Marine field representative with questions, or contact us at [email protected]. Mercury will do its best to help find answers, whether you're seeking general information or wishing to discuss legal proposals, or if you're seeking information regarding ethanol-tolerant materials.

What are ethanol and ethanol-blended fuels?

Ethanol for fuel is highly refined beverage (grain) alcohol, approximately 200 proof, that can be produced from natural products such as corn, sugar cane and wheat. New technology will allow ethanol to be made from "cellulosic" feedstocks including corn stalks, grain straw, paper, pulp, wood chips, municipal waste, switchgrass and other sources. Ethanol used for fuel has been "denatured," or rendered unsafe to drink by the addition of a hydrocarbon (usually gasoline). The ethanol-blended fuel E-10 refers to fuel that contains 10 percent ethanol and 90 percent gasoline. Similarly, E-85 refers to fuel that contains 85 percent ethanol and 15 percent gasoline. E-85 is intended only for engines specially designed to accept high-ethanol content fuel blends, such as the Flexible Fuel Vehicles (FFV) made by some car companies.

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How is ethanol made?

In the U.S., ethanol is typically produced by removing the starch or sugar portion of corn and fermenting it. The fermented starch is then distilled into alcohol. Excess water is removed, resulting in very pure - 200 proof - ethyl alcohol (ethanol).

In some parts of the world, ethanol is made from a variety of raw materials. For example, sugar cane is used to produce ethanol in Brazil, while sugar beets and wheat straw are commonly used in Europe.

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What are the characteristics of ethanol?

Ethanol is an oxygenated hydrocarbon compound that has a high octane rating and therefore is useful in increasing the octane level of unleaded gasoline. The EPA, the agency responsible for setting some of the requirements for all gasoline used in the U.S., has allowed the use of ethanol in gasoline at levels up to 10 percent as an octane enhancer and to provide beneficial clean-burning combustion characteristics that help improve some emissions.

Ethanol is hygroscopic (it has an attraction for water) and will more readily mix with water than with gasoline. It has different solvency behaviors than does gasoline, which allows it to loosen rust and debris that might lay undisturbed in fuel systems. And it can more readily remove plasticizers and resins from certain plastic materials that might not be affected by gasoline alone. Loose debris will plug filters and can interfere with engine operation. Additionally, ethanol is corrosive to some metals, especially in combination with water. Although gasoline does not conduct electricity well, ethanol has an appreciable capability to conduct electricity and therefore can promote galvanic corrosion.

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What is MTBE and why is it being replaced?

MTBE is the chemical shorthand description for methyl tertiary-butyl ether. MTBE is another oxygenated hydrocarbon compound that has a high octane rating. It was initially a preferred compound widely used for octane enhancement as a replacement for leaded compounds in gasoline. When the EPA developed regulations requiring oxygenated gasoline to help reduce smog in several areas of the country, MTBE was the most commonly used compound to supply the additional oxygen, while ethanol was chosen for this purpose in the Midwest region of the country. Recently, most states have banned the use of MTBE because of its tendency to work its way into ground water systems, usually from leaks and spills, as an undesirable contaminant. Ethanol is being used as a replacement.

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Does ethanol affect horsepower or fuel-efficiency?

Ethanol has a heating value of 76,000 BTU per gallon, which is approximately 30 percent less than gasoline's heating value (which is approximately 109,000 to 119,000 BTU/gal). The result is E-10 gasoline which should yield slightly lower mileage - a decrease of approximately 3 percent. Fuels containing higher levels of ethanol will have a corresponding reduction in mileage. For example, E85 fuels produce mileage approximately 30 percent less than gasoline.

The octane rating of pure ethanol (200 proof) is about 100 and is therefore useful in elevating the octane value of gasoline. In E-10 blends the presence of ethanol provides about 2.5 to 3 percent of the overall octane rating. The effect on engine horsepower is determined by the octane result of the blended fuel. Care should be taken to select fuels having the octane rating recommended for the engine as indicated in the owner's manual for proper operation.

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Are Mercury engines compatible with ethanol fuels?

The fuel-system components of Mercury engines will withstand up to 10 percent ethanol in gasoline - the maximum level currently allowed by the EPA in the U.S. There are some efforts to establish E-20 (20 percent ethanol mixed with 80 gasoline) for use in some areas, but that will require agreement from EPA to grant a waiver. Part of the EPA waiver process will require verification from studies that demonstrate that higher levels of ethanol do not create problems with fuel-system materials or operation of hardware. E-20 has not been extensively studied by Mercury and is not acceptable for use in Mercury products. E-85 fuels must not be used in any Mercury engines and could seriously damage current Mercury products. It is not legal in the U.S. to market any ethanol fuel as gasoline if it contains more than 10 percent ethanol.

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Will the use of fuels containing ethanol void my engine warranty?

Fuels containing up to 10 percent ethanol are considered acceptable for use in Mercury engines. Fuels containing higher levels of ethanol are not considered acceptable for use, and the use of fuels containing ethanol higher than 10 percent can void the warranty.

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What about the fuel-system components on the boat?

It is important to follow boat manufacturers' recommendations when selecting appropriate fuels. Use of an inappropriate fuel can result in damage to the engine and boat components that may require repair or replacement. Fuels with ethanol can attack some fuel-system components, such as tanks and lines, if they are not made from acceptable ethanol-compatible materials. This can lead to operational problems or safety issues such as clogged filters, leaks or engine damage.

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Can ethanol-blended fuels affect the performance of traditional carbureted two-stroke outboards?

Two-stroke outboards should experience little or no decrease in performance due to gasoline fuels containing up to 10-percent ethanol when operated according to Mercury's standard recommendations. When gasoline with ethanol is used for the first time after a fuel changeover from MTBE, the tank must be completely free of water prior to introduction of gasoline with ethanol. Otherwise, phase separation could occur that could cause filter plugging or damage to the engine. (It is probably better for a boat owner to fill the fuel tanks with ethanol fuel for the first time when the tank is low on fuel, but that is not critical. There should be no difficulties if the tank is clean and free from water. If the tank is not free from water, a partial load of fuel will more easily phase separate because with less ethanol in place it takes less water to cause phase separation. The important thing for boaters to concern themselves with is the presence of water in their tanks.)

If an engine is a 1990 or older model, frequent inspections of all fuel-system components are advised to identify any signs of leakage, softening, hardening, swelling or corrosion. If any sign of leakage or deterioration is observed, replacement of the affected components is required before further operation.

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How does ethanol affect my fiberglass fuel tank?

Fiberglass tanks manufactured prior to 1991 may not be compatible with gasoline containing ethanol. It has been reported that, in the presence of ethanol, some resins may be drawn out of fiberglass and carried into the engine where severe damage could occur. If an older fiberglass tank is used, check with the manufacturer to determine if gasoline with ethanol can be safely used.

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Are older fuel lines prone to failure? What about gaskets?

During the 1980s, many rubber components for use in fuel systems were developed to withstand exposure to fuels containing ethanol. If rubber components in a fuel system are suspected to be of this vintage or older it may be advisable to replace them with newer ethanol-safe components before using fuels containing ethanol. Check with the manufacturer for advice or frequently inspect these fuel-system components for signs of swelling or deterioration and replace if problems are noted.

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Ethanol is replacing MTBE in my region? What should I do?

Before gasoline with ethanol is introduced to your fuel tank, ask your boat manufacturer if any special precautions should be considered with the use of fuel containing ethanol. Check for the presence of water in the fuel tank. If any is found, remove all water and dry the tank completely. As a precaution, it is advisable to carry a few extra filters in case filter plugging becomes a problem during boating.

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Should I add an additional fine-micron filter to the system to prevent debris from entering the engine?

The addition of another filter to the system will create another possible flow restriction that can starve the engine of fuel. Mercury already provides the appropriate level of filtration to protect the engine from debris.

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How can a marina prepare for the change from MTBE to ethanol as the fuel oxygenate?

Check with the manufacturer to make certain the tank and lines won't experience problems with ethanol. Inspect the tank for water and, if present, pump out all water and thoroughly clean the tank. Install ethanol-compatible filters. The tank should be less than 20 percent full before adding the first load of fuel with ethanol.

This will help avoid difficulties of dealing with and selling fuel that is a mixture of two different fuel blends to a boater who may have a third blend in the tank. And the marina is dealing with larger stationary tanks that will not allow the two different blends to mix very easily. Ethanol and MTBE should be compatible with each other chemically, but different amounts are used for oxygenation and octane adjustment purposes, and having a tank with two different chemical compounds floating around trying to redistribute could produce unpredictable results. With a tank containing less than 20 percent fuel to begin with, there will be less potential for stratification or other unexpected behavior to enter into the picture. This is consistent with typical practice in the oil and fuel industry and is intended to minimize interaction between blends with different chemical content. It is critical that marinas know their tanks are free from water.

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What is phase separation, and how do I deal with it?

If significant amounts of water are present in a fuel tank with gasoline that contains ethanol, the water will be drawn into the fuel until the saturation point is reached for the three-component mixture of water + gasoline + ethanol. Beyond this level of water, phase separation could cause most of the ethanol and water to separate from the bulk fuel and drop to the bottom of the tank, leaving gasoline with a significantly reduced level of ethanol in the upper phase (see Figure 1 below). If the lower phase of water and ethanol is large enough to reach the fuel inlet, it could be pumped directly to the engine and cause significant problems. Even if the ethanol water phase at the bottom of the tank is not drawn into the fuel inlet, the reduced ethanol level of the fuel reduces the octane rating by as much as 3 octane numbers, which could result in engine problems.

The level at which phase separation can occur is determined by a number of variables, including the amount of ethanol, the composition of the fuel, the temperature of the environment and the presence of contaminants. It is very important (A) that the system is inspected for significant quantities of water in the tank before using gasoline with ethanol and ( to limit exposure of the fuel tank to excess water. If phase separation has occurred, it is necessary to completely remove all free water from the system and replace the fuel before continuing operation. Otherwise, engine problems could occur.

Figure 1: Sample of fuel from fuel tank in which phase separation has occurred. The upper phase is gasoline with a reduced level of ethanol. The lower level is a mixture of ethanol and water.

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Is an additive available that can prevent phase separation?

There is no practical additive that can prevent phase separation from occurring. The only practical solution is to keep water from accumulating in the tank in the first place.

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Are there any additives that can allow the phase-separated mixture to remix when added to the fuel tank?

No, the only way to avoid further problems is to remove the water, dispose of the depleted fuel, clean the tank and start with a fresh, dry load of fuel.

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Is there a simple solution to water condensation in the tank as a result of ethanol?

It is best to maintain a full tank of fuel when the engine is not in use. This will reduce the void space above the fuel and will reduce the flow of air in and out of the tank with changes in temperature. This will reduce condensation on the internal walls of the tank and will limit exposure of the ethanol in the fuel to humidity and condensation.

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What should be done when storing boats with ethanol-blended fuels for extended periods?

Follow the instructions for normal storage preparation found in the owner’s manual or operations guide. When preparing to store a boat for extended periods of two months or more, it is best to completely remove all fuel from the tank. If it is difficult or not possible to remove the fuel, maintaining a full tank of fuel with a fuel stabilizer added to provide fuel stability and corrosion protection is recommended. It is best to add the stabilizer and fuel treatment to the tank at the recommended dosage, running the engine for 10 minutes to allow the system to be cleaned, shutting off the fuel valve to interrupt the fuel supply and allow the engine to run until it stops, topping off the tank until it’s full to reduce the amount of exchange with the air that might bring in condensation. Do not cap the tank vent and do not fill with fuel to the point of overflowing. Some extra space should be maintained in the tank to allow for expansion and contraction of the fuel with temperature changes. A partially full tank is not recommended because the void space above the fuel allows air movement that can bring in water through condensation as the air temperature moves up and down. This condensation could potentially become a problem.

Mercury Marine Fuel System Treatment & Stabilizer can help maintain fuel systems in storage. It contains oxidation inhibitors to reduce oxidation and gum formation, metal chelating agents to protect metal components from corrosion, water absorbing agents to reduce the presence of free water, and dispersants to help suspend and disperse debris. When placing the boat back in service, be sure to reopen the fuel valve to the engine.

[lucky]

I used premium gas but when it got close to 5.00 a gallon i thought i would switch to 87 octane. I thought i could use a boost to get the higher octane. I got so many different answers and peoples opinion i had to call merc them self. The said to use 87 octane and thats it no higher. They said that my '99 60 hp does not need it. They also said that the higher octane could do damage because it burns at a different temp. It has something to do with the compression ratio. I would use a stablerliser and the product called merc clean

[hydro]

Good advice Lucky. The urban myths surrounding the benefits of premium and non-oxy fuel run wild on this forum.

[boatfixer]

100% agreed Hydro. Its no different than any of us trying to run Sonoco race gas in our own vehicles.

[delcecchi]

With all due respect, I don't believe the part about premium fuel causing damage to be true.

And if you read the FAQ posted above it sounds like there are a host of reasons to avoid ethanol in gasoline in a boat. Many of the concerns, from phase separation to material incompatibility, would go away if the gas is non-oxy.

Seems to me that last summer, non-oxy was like 25 cents more than regular. But that easily could be incorrect. Someone in the area could look next time they stop since most of the stations at least the ones north of virginia seem to have non-oxy pumps.

[whitebassman]

If at the pump it has the nonoxy sticker, stating use for collectore vehicles, small motors, boats, etc. Is that implying that the 91 octane IS nonoxy? I ask because the sticker is not always side by side with the 91 octane label, usually is above it though.

I guess I would go with mfr instructions, especially if you are still under warranty, then they can't blame you for running nonrecommended octane. I agree with the Stabil though.

[delcecchi]

If at the pump it has the nonoxy sticker, stating use for collectore vehicles, small motors, boats, etc. Is that implying that the 91 octane IS nonoxy? I ask because the sticker is not always side by side with the 91 octane label, usually is above it though.

I guess I would go with mfr instructions, especially if you are still under warranty, then they can't blame you for running nonrecommended octane. I agree with the Stabil though.

I presume that is true. That is what it says at the pump when I buy it.

[BobT]

Thought I'd share my experience this year. Maybe I'm flirting with a disaster but....

Last fall when I parked my boat for the winter, I didn't do anything special to "winterize" my outboard except to replace the lower unit gear oil. When I parked it, it had about 3/4 tank of fuel. I use 87 octane per motor nameplate recommendations and in MN that means 10% ethanol blend. In many parts of MN I believe 87 octane has been a 10% ethanol blend since the 80s so it isn't something new and my motor is a 1998 model Johnson 90hp 2-stroke so when the motor was built, ethanol was not a stranger.

I made sure my battery fluids were topped off and then put the battery charger on my batteries (deep cycle and starting) twice during the winter to make sure they were charged and both times the charger indicated full charge almost immediately.

Yesterday, hooked up my earmuffs, squeezed the fuel bulb until I felt pressure and turned the key. The motor starter turned for about five seconds and the motor fired and idled with a little choke help for the first minute or so until it warmed up a bit.

Last week I put the battery back in my lawn mower and hit the key. It too started right up and in fact, I didn't have to feather the choke on that. It's a 14hp Briggs from 1999 and when I parked it last fall it had about 1/2 tank of 87 octane fuel. Again, no Stabil or Sea Foam or any other fuel additives were used. That lawn mower is stored under a lean-to all winter so its not even completely protected from blowing snow.

This is the way I've been doing things for the past 30 years. I'm either really lucky or there's more hype about fuel going bad than reality.

[WaveWacker]

I had a completely opposite experience. 87 octane and that's it in the boat. Just through it in as they didn't have non-oxy and forgot to juice it up with some SeaFoam. That was around the middle of July (a couple years ago) and didn't get the boat back out until Labor day. Yep, semi-plugged up carb. I ran it down to the dealership right away and they opened things up by shooting some air through the line so I lucked out that they didn't have to tear the whole carb apart. I was told to try to run non-oxy and also some SeaFoam or Stabile every time I put gas in. So that's what I've been doing and it's been working.

Also been doing that with the chain saws, splitter, lawn mowers etc. and had great luck firing them back up. It's been working for me so it's worth the extra price to me. Just my experience however.