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A Complete Guide to Buying Boat Fuel
A Complete Guide to Buying Boat Fuel

Buying boat fuel is not the same as buying car fuel. There are more than three generic types, and each boat has its own needs. 

You could even use different kinds of boat fuel for the same kind of boat.

But, how do you know what kind of boat fuel to use for your boat? Well, there are a few ways to tell what you should use.

Keep reading to learn the ins and outs of all the different kinds of boat fuel.

Choosing Boat Fuel

All of the current boat models that have outboard, sterndrive, and inboard gasoline engines use fuel with no more than 10% ethanol. Accordingly, this fuel is known as E10.

You should never use E15, E85, or another type of fuel with a higher concentration of ethanol. Even if nothing immediately goes wrong, using this gas will immediately void the warranty on the vehicle.

The fuel system for these kinds of boats can't tolerate higher ethanol blends because of how corrosive they can be. 

In fact, most older vessels can't handle this corrosion at all. Older boats were created before there was any ethanol in fuel. So, you can't use ethanol-based fuel at all unless you update the boat's fuel system.

No matter what boat you're filling up, you need to pay attention to the signs at the pump. The most popular fuel across the country is E15, so this is the kind that's not always properly labeled.

When possible, you should avoid ethanol completely.

Ethanol attracts water, so it absorbs the moisture from the water that your boat is in. That water goes through the fuel tank vent system and may settle out the fuel, separating it at the bottom of the tank.

All in all, this water could cause damage to the engine.

Read the Manual

The boat's manual is the key to understanding what kind of fuel your boat needs. It should specify a minimum fuel octane rating. 

If your boat has a high-performance engine, it may need a higher octane rating than the standard 87 octane.

If you have to use fuel with a higher ethane percentage, you should invest in a 10-micron water-separating fuel filter. This filter lies between the engine and fuel tank to keep the water (and other contaminants) out of the engine.

Again, the boat's manual should let you know what the best filter size is.

What About Buying Boat Oil?

Getting the right boat oil is just as important as getting the right boating fuel. Just like with the boat fuel, your boat's manual should tell you what kind of oil to use.

If your boat has a four-stroke engine, the oil that you use needs to meet FC-W certification. (The oil will have an FC-W symbol/label if it meets certification standards.)

Without the FC-W certification, the oil that you're using may not have rust protection. Oils with the certification have a higher minimum viscosity level. This prevents the oil from thinning out.

When it comes to oil maintenance and filter changes, you should consult your boat manual.

Keep in mind that car oil and boat oil are very different. You can not interchange these kinds of oils without causing damage to the engines.

Buying Boat Fuel

There are several different kinds of boat fuel for you to choose from when you're at the pump. The kind that you choose is going to depend on the kind of motor that your boat has.

For example, a small boat like a pontoon will require gasoline. Alternatively, you could fill these kinds of boats up with a mix of gasoline and two-cycle oil.

On the other hand, larger boats may require diesel.

Those boats that fall in between may require any of these three types of fuel. The exact choice will depend on three things:

  1. The type of boat you're fueling
  2. The size of the boat you're fueling
  3. The motor that the boat has

Before you jump into each of these fuel types, you should make sure that you know these details about your boat. Without this information, you aren't going to know which one to choose.

What Fuel Should I Use for Outboard Boat Motors?

We're going to address outboard motors first. It seems like this is the most controversial fuel option for boaters.

Our top pick for boats with outboard motors is ethanol-free gasoline. If you go on your boat often and have enough money to invest in it, you should really consider avoiding ethanol.

If you don't, there are two low-ethanol options that you can choose between:

  1. E10 fuel
  2. E15 fuel

E10 fuel has 10% ethanol, while E15 has 15% ethanol.

E10 is compatible with modern engines that were made or updated within the past decade. Although E10 is better than typical boat gasoline, it still contains some ethanol. Therefore, it can still cause some problems.

E10 can reduce your boat's pollution into the environment. But, the remaining 10% of ethanol can corrode rubber, harm fiberglass, loosen fuel debris, and clog your fuel line.

Although, using E10 is cheaper in the short term.

As you can probably assume, E15 is even worse. E15 is worse for the environment and can do even more damage to your engine. Boats that use E15 exceed EPA admission standards as well.

Overall, you should use ethanol-free gasoline if you can. However, you should only opt for E10 if you're looking for a cheaper option.

What Fuel Should I Use for Small Personal Boats?

Small, personal boats offer a larger selection when it comes to choosing gasoline. However, you should still take the time to see which kind of fuel is the best for your boat in particular.

Before making any decisions, you should check what your manufacturer recommends. They may ask you to use a specific kind of fuel or specific content of ethanol in the fuel.

Most small boat-owners end up choosing between gasoline, diesel, and red diesel. 

What Fuel Should I Use for Pontoon Boats?

Because pontoon boats are so variable, you should always refer to the manufacturer's recommendations. 

Most pontoon boats have an outward motor. If this is true for yours, you can use E10 or non-ethanol fuel like we discussed earlier.

Some pontoon boats can operate off of the same fuel that you use in your car.

Considering the kind of fuel that your pontoon boat uses is important before making the purchase. Going with a cheaper fuel type could save you a lot of money over time.

What Fuel Should I Use for Large Commercial Boats?

The larger a boat is, the more likely it is that you're going to need to get special fuel. There are two common types of fuel that large commercial boats use:

  1. Marine gas oil (MGO)
  2. Marine diesel oil (MDO)

Marine gas oil is a blend of light-cycle gas oil and aromatics, while marine diesel oil has heavy fuel oil.

Oftentimes, typical marinas won't have these two kinds of fuels. Although, most everyday boaters don't use these kinds of fuels.

Unless you have a cruise ship sitting in your garage, it's not likely that you'll need access to this kind of fuel.

Boat Fuel Buying Tips

Buying boat fuel isn't cheap. No matter how much you make, the cost of boating fuel can sting.

It's rare that a captain looks forward to filling up the tank.

But, there are a few safety tips and tricks that you can use to save time and money while you're filling up.

1. Know the Size of Your Boat's Fuel Tank

If you don't know how big your boat's tank is, you won't know how much fuel need actually need. 

Most people find that the fuel gauge is the first thing to go on their boat. So, you may not be able to tell how much fuel you have or how big your tank is in total.

But, you should do your best to determine how much fuel you need when. Even if you can only get a ballpark range of fuel, this can help you save time and money at the pump.

2. Check in With Your Boat

Your boat will tell you when it needs some fuel. While the fuel gauge is a good indicator (if it works), there is another indicator that we're talking about.

There is a distinct sound that your boat tank will make when it's on the last gallon of fuel. Once you hear that sound once, you'll be able to distinguish it in the future.

3. Never Top Off Your Boat's Fuel Tank

Just like when you fill up your car, you should never top off your boat. When in doubt, stop the fuel from pumping.

Unfortunately, not all pumps work like gas pumps for your car. They may not stop when your boat is full. 

So, you'll end up filling the boat until you see fuel coming out. At that point, you're wasting fuel, time, and money.

One of the best ways to determine whether you're close to filling up the tank is by listening as you're getting fuel. You'll be able to tell whether or not your tank is close to full.

4. Avoid Propping the Handle

If you have a habit of propping the pump handle while you're filling up your boat, you're rolling the dice. Propping, also known as chalking, is extremely dangerous.

It takes a long time to fill up the fuel tank, but that doesn't mean that you should get lazy with the pump.

When you're fueling your car, you can get away with doing this. But, it's different for boats.

The pump can easily come out of place and cause the fuel to spill outside of the tank. Then, you're wasting time, money, and fuel. And, you're probably making a mess.

5. Skip the Boat Soap

There is a misconception in the boating community that says that you should pour dish soap on top of any gas that you spill. Most often, people think that pouring Dawn soap over the gas will undo the damage that you've just done.

It's easy to believe this misconception because the fuel disappears when you pour the soap over it. But, all the soap does is make the fuel denser than it was previously. So, the fuel will sink to the bottom of the water.

This is actually worse.

If the fuel floated on top of the water, it could have gotten evaporated by the heat from the sun. Once it floats to the bottom, this can't happen. So, the fuel will stay on the bottom of the ocean/lake floor and sit there for decades.

If you do ever spill boat fuel, you should ask for a fuel absorbent pad, also known as a fuel sorb. In fact, you may want to carry one of these with you regularly.

These pads can help you clean up the fuel faster than the sun would evaporate it. And, if you aren't able to get all of it up, the sun can take care of the rest.

6. Avoid Fire Sources Around Fuel

Just like with fuel for cars, you should avoid putting any fire sources next to the fuel. 

While you're fueling your car, you should keep smoke away from the gas tank. You should also shut your tank off before filling it up.

If you have trouble remembering, write the note on a piece of tape and place it right next to where you fill-up the tank. This will kindly remind you to keep these things away from the tank next time you're filling it up.

Join Our Boating Club to Learn More

When it comes to boat fuel, you have a lot of options. However, there is always a better option to choose with each kind of boat.

If you're interested in learning more about boating, you should join our boat club. You don't have to own a boat to become a member, and it's a great way to learn about boating before you make a commitment.

Learn more about our boat club membership and apply today!