Boat Fuel Types: What Fuel Type for My Boat? (Newbie Guide)

With a small, personal boat or pontoon, choosing the right type of fuel is downright confusing for many people.

You will have to choose between various ethanol levels, mixing oil with your fuel, and even deal with diesel. Most boat owners feel completely overwhelmed by trying to select what is right for their boat.

What fuel fits your boat best?

A lot of fuel choices come down to your type of motor. Small personal boats and pontoons will benefit from gasoline and ethanol, but larger commercial boats may all require diesel. Others may require any one of the three, depending on your motor, size, and type of boat.

If you need a little help deciding what type of fuel to put in your boat, this complete guide for newbies should give you a great starting point to build up your boating knowledge.

What Type of Fuel Do Outboard Boat Motors Use?

There is a lot of debate over what type of fuel an outboard motor should use.

Avid boaters who don’t mind dropping more money on their fuel costs should really consider using ethanol-free gasoline.

With this method, you can ensure that your motor and boat will last for years to come.

E10 Fuel

However, many people prefer to crunch their numbers as tightly as possible. Running E10 (a fancy way of saying ten-percent ethanol) is still an acceptable way to give your boat what it needs.

It should be compatible with any engines created in the past decade or so. Ethanol is introduced into fuel as a way of reducing pollution. This high-grain alcohol may not be the kind you want to consume, but it does help to lower hydrocarbon emissions.

In low quantities, it can be beneficial to run E10 fuel in your small personal boat. You can run your boat off of E10 fuel to save costs right now, but there could be some long-term implications for doing so.

Ethanol is well-known for being a solvent that can quickly corrode rubber and fiberglass. It can also loosen the debris that may be in your fuel and lead to a clogged fuel line.

Only fill up with the amount that you need to help avoid some of these negative side effects of using E10 in your boat.

As you might imagine, ethanol can do some serious damage to your boat over time. It can break down a strong fiberglass frame and puncture a hole in the tank. Beyond that, ethanol also tends to attract water.

If a boat is docked for more than ninety days, experts typically recommend draining the ethanol-gasoline from your tank.

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E15 Fuel

Keep in mind, there is a plenty of controversy surrounding gasoline with ethanol levels higher than ten percent. Many politicians are lobbying for the sale of E15 (fifteen percent ethanol and eighty-five percent gasoline). However, the National Marine Manufacturers Association has been very outspoken about the potential damages associated with E15:

  • E15 can not only damage your engine, but it is also bad for the environment.
  • The Department of Energy’s National Renewable Energy Laboratory found that E15 caused boats to exceed EPA admission standards.
  • Some outboard motors may specify a different type of fuel.

Make sure to double-check your owner’s manual for the specifics regarding your outboard motor just in case.

When given a choice at the pump, ethanol-free is a great way to go, but E10 will also work. Make sure that you verify exactly what you are getting at the pump, as many places will not have the pumps clearly marked. Check with the sales associate to make sure that what you find is acceptable for your boat.

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What Is The Best Gas for Outboard Motors?

The best gas for outboard motors will depend on the specific make and model that you purchase. Identify your manufacturer’s specific instructions in the owner’s manual before you make a final decision about what to put in your boat.

For the most part, outboard motors will run on E10 gasoline (ten percent ethanol and ninety percent gasoline).

Keep in mind that there are some risks to using ethanol-blended fuels. They can sometimes cause corrosion in the tank and eat through fiberglass finishes on the boat. You must be careful to ensure that you do not have too much water in the tank with your ethanol.

Ethanol-free fuel is the best way to go for most outboard motors. In many cases, you can use the same fuel in your boat as you do in your personal vehicle. Be sure to check with the local marina or wherever you typically fill up your boat to see what type of ethanol-blended fuels they offer.

However, some boats do run on diesel engines. These engines tend to be more powerful and use less diesel compared to how quickly you may burn through E10 gasoline. A diesel engine is a more efficient choice for many boaters, particularly if you have a longer boat.

The best gas for your outboard motor truly depends. Consult your owner’s manual to see what they recommend for maintaining your boat and engine long-term.

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Can I Switch to Ethanol Gasoline?

Many people wonder whether they can make the transition from using ethanol-free fuel to using E10 in their boats. Maybe they are looking for a way to save a few dollars, or perhaps the marina stopped carrying ethanol-free fuel. No matter what the reason, the question remains: can I make the switch to ethanol?

Adding ethanol into the engine of your boat can be the source of some major problems at first. Ethanol is a brand-new solvent that you are introducing into your boat. As a result, it tends to loosen debris that has built up inside the tank and the fuel system. This can, in turn, clog your fuel line.

If you want to make the switch to ethanol gasoline, there are a few things you should do beforehand:

  • First, you should check for any water inside your fuel tank and pump it dry if you find it. Examine the contents of what you pumped out to determine if the tank needs to be completely cleaned using a quality product designed for this purpose.
  • Once you take care of this, completely fill up your tank with E10 fuel to absorb any remaining water left in the tank.

Ethanol-blended fuels like E10 can absorb a certain amount of water that is found in your tank. However, it can be problematic if there is too much water in your tank for the E10 to absorb.

When the fuel and water begin to separate, this is when the ethanol becomes the most corrosive and damaging to the tank of the boat.

Most boating professionals recommend cycling your fuel every ninety days. If you do not think that you will use all of your fuel over the next three months, it is typically better not to fill it all the way up. You should also try to drain some of the fuel from the tank if you are going to be storing the boat for the winter.

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What About Smaller Personal Boats?

Smaller personal boats offer you more selections when it comes to what type of fuel should be used. This is an important question to consider when you are first weighing the decision to purchase a small boat for your personal use. Once you make the purchase, you should stick with using the type of fuel recommended by the manufacturer. However, you do have some choices, including gasoline, diesel, and even red diesel.

Consider how big you want your boat to be when making the initial purchase. Smaller boats that range in size from thirty to forty feet will typically offer options for both gas engines and diesel engines:

  • Diesel tends to be more expensive both in terms of the motor and the fuel itself.
  • It also typically produces a louder engine that may detract from your overall boating experience.

Slightly larger boats that exceed forty to forty-five feet in length will almost always come with diesel engines.

They require the extra horsepower and torque that comes from a diesel engine to run smoothly through the water:

  • According to some experts, diesel has roughly ten percent more energy potential than gasoline because the engine runs more efficiently.
  • This means that you can go further on less fuel. With these savings in mind, it may help to balance out the price difference between gasoline and diesel at the pump.

Red diesel is widely considered to be the same as regular diesel, but it has a red additive included to mark it for a specific use. It is intended to be used for agricultural equipment and other off-road vehicles. In the past, boat owners were allowed to use this less-taxed fuel in place of white diesel.

However, the UK has now revised those laws and requires most pleasure-craft boaters to purchase the white diesel.

While there is no real difference between white diesel and red diesel apart from the color, there is a significant price difference. Red diesel is taxed less heavily than white diesel. If you live on your boat, you can still use red diesel to fuel your home. Most others will be required to fuel their boats with the higher-taxed white diesel moving forward.

When Should I Add Oil to the Fuel?

Older two-stroke outboard motors on your smaller personal boat may require you to mix the fuel and oil on your own. They typically have a smaller tank located near the engine for you to pour two-stroke oil into.

Some people find that they prefer to mix their own fuel, even if the boat motor offers the capability of pre-mixing it for you. Check with your owner’s manual to see what is recommended.

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Finding the right ratio of oil to fuel is another tricky problem for individuals who have small boats. Getting the math wrong can have serious consequences, including a smoking motor that coughs and splutters. You could even do some major internal damage to your motor if you aren’t careful enough.

Trying to calculate the total amounts at the pump can slow you down, so many people prefer to mix their oil with gasoline in advance.

You may even need to use more oil in the very beginning if you are just purchasing the boat:

  • Some engines will require a 25:1 ratio for a specific length of time following your purchase.
  • The two-stroke engines that are found in most new personal boats require a 50:1 ratio.
  • For the basic 50:1 ratio, this means that you will need to use 2.6 fluid ounces of oil per gallon of gas added to your tank.

If you are trying to figure out the proper amounts for an older used boat, it is recommended that you check with the manufacturer for a specific recommendation.

What Type of Fuel does a Larger Commercial Boat Use?

As the boat increases in size, the type of fuel that it uses tends to stray away from the gasoline and diesel that you may be used to.

Two major types of fuel can be used in a large commercial boat: marine gas oil (MGO) and marine diesel oil (MDO):

  • Both of these fuels are considered to be distillate fuels, used primarily in high and medium powered boats
  • Marine gas oil is comprised of a blend of light cycle gas oil and aromatics. It may also contain some waste products such as used motor oil.
  • On the other hand, marine diesel oil is an entirely different sort of fuel than traditional diesel that you may use to power your truck. Unlike this more common form of diesel, marine diesel oil contains heavy fuel oil.

The chances are that your local marina does not have these two types of fuel readily available.

Many smaller marinas only carry the E10 gasoline or diesel that cater to smaller personal boats.

You would have to head to a much larger marina that could accommodate these big commercial boats if you wanted to find this sort of fuel.

Can Boats Run on the Same Gas as Cars?

Are you looking for a new way to make gassing up your boat more convenient?

The good news is that many of the smaller personal boats on today’s market can run on the same gas as your vehicle. You must make sure that you are paying attention to what is available at the pump if you want to get away with this, though.

Ensure that the pump you use has either ethanol-free gasoline or E10 fuel. This is relatively common, but there may be times when you encounter a gas station that sells only E15.

Due to the damage, this can cause your engine and the high emissions rates it causes, E15 should be avoided at all costs.

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A gas station that sells E15 must have the pump marked so that customers know they are purchasing a higher ethanol content with their gasoline. It is a federal law violation to try to use E15 fuel in your boat.

It may save you a tremendous amount of money at the pump, but putting E15 fuel into your boat simply is not worth it.

What Kind of Gas do Pontoon Boats Use?

Pontoon boats can be manufactured in a variety of ways, so it helps to know exactly what your make and model recommends. Most of the boats that fall into this category have a small outboard motor to propel them through the water. The larger the pontoon is, the more powerful this outboard motor is required to be.

For the most part, pontoon boats can be operated off of the same unleaded fuel that you would use in your car. You also want to keep the ethanol content of the fuel in mind when you are filling up your pontoon boat. E10 (ten percent ethanol) is the maximum amount of ethanol that you will want to use in your motor.

Higher ethanol content is available, but it is not approved for use in boat motors. Avoid filling up at pumps marked as E15 because this could damage the motor on your pontoon.

If you have an older pontoon model, you may have a two-stroke outboard motor. This requires a little bit of extra work in the way of adding two-stroke injection oil into a separate tank somewhere near the engine. The specific ratios of oil to gasoline will vary, but most people estimate that you should have them in a 50:1 ratio. A newer motor may require double that ratio at 25:1.

Final Thoughts: Choosing the Right Type of Fuel

There is a lot of conflicting information available about what might be best for your boat. Small personal boats, pontoons, and even larger commercial boats may all require a different type of fuel and oil. Understanding what each one requires is the first step toward making your boat last for the long haul.

With some of these top questions answered, you can be better informed about making decisions for your boat!

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