How Much Is Gas for A Boat? All About The Boat Fuel Cost

Despite modern electricity and other fuel options, gasoline is still among the most common power sources for numerous vehicle engines, including boats and ships. 

Marine gas is further categorized into smaller groups and comes at different price ranges, which raises concerns about the money you must spend to operate your boat for extended periods. Let’s check the current gas prices for boats in more detail.

How Much Is Boat Fuel?

According to the latest update on the marine gas price of Waterway Guide (20/10/2023), each gallon of marine gas costs more than $4. The exact price varies with the location, type of gas, and the size of your boat.

speedboat petrol station

Other factors that influence the total costs of your boat gas:

Gas Type

Most boats, especially large vessels of more than 45 feet, use gasoline rather than diesel. 

Your choice between 2 main types of gas, non-oxygenated and oxygenated gasoline, will determine the fuel cost. Oxygenated gas includes Ethanol and other additives to emit as little carbon monoxide as possible – quite the opposite of non-oxygenated gas, which minimizes corrosion but is much less clean. 

Most manufacturers recommend using non-oxygenated gas for older boats, which means you might have to spend more. Not to mention, some old gas tanks require you to add lead substitutes to protect their cylinder heads, and that’s not something every marina provides.

Octane Rating

Octane rating refers to the gas’s resistance level against knocking under extreme pressure. You will easily find the related number in the owner’s manual or by contacting the manufacturer directly.

Suppose you own a high-performance fishing boat or speed boat; then buying gasoline with a higher octane level is the only way to guarantee optimal operation. The stability of high-octane gas also contributes to its higher price.

The Boat Size & Mileage

Smaller boats need fewer gallons of gas than bigger ones. Similarly, newer boats offer much better gas mileage than older models, partly due to technological advancements, resulting in lower fuel costs during the trip. Unfortunately, calculating a boat’s fuel efficiency is not as easy as it sounds. 

Speed boat size
Speed boat size

Water affects the boat’s operation significantly, and the fluctuating water conditions also result in varying boating experiences. As such, you will have to spend much more money for the same distance on water than on dry roads. That also means you cannot approach fuel calculations for boats the same way you would for lane vehicles.

We suggest determining the gallons of gas per hour using the fuel type and your boat’s horsepower. You may also divide the horsepower by 10 to calculate the MPG (e.g., a 250-HP engine needs 25 gallons an hour at its peak output), but note that this number is not fixed. Wave conditions, hull conditions, wind speed, and engine RPMs all have a say.

Cruising Speed

Higher speeds equal more fuel burned, and heavier boats also use much more gas than lighter ones. But the great news is that you have total control over your own cruising speed.

Pay attention to the vessel’s RPM (revolutions per minute) and fuel flow rate to determine your best cruising speed. The sweet spot is usually between 3,000 and 3,500 RPMs, although you might notice significant increases or decreases in certain boat types. For instance, pontoon boats are associated with leisure trips and usually hit 30 MPH on average, thereby reducing the fill-up frequency, while speedboats have to drop by gas docks much more often due to their high speeds. 

How to Calculate The Cost of Marine Fuel By Yourself

Most people often measure fuel efficiency by calculating the amount of consumed fuel (in pounds) per horsepower produced every hour – a metric referred to by boaters as “brake-specific gas consumption.”

Step 1. First, identify the fuel type your boat engine uses. Some examples:

  • Gasoline weighs about 6.1 pounds a gallon. A 4-stroke engine burns approximately 0.5 pounds of fuel for every horsepower unit per hour. 
  • Diesel weighs approximately 7.2 pounds a gallon, burning about 0.4 pounds of fuel for each horsepower in one hour.

Step 2. Now we have the formula to calculate maximum gas consumption: 

  • GPH (Gallons Per Hour) = Horsepower x Specific Gas Consumption/ Gas Specific Weight
  • Let’s say your diesel engine has a horsepower of 200 HP; the formula is as follows: GPH = (200 x 0.4)/ 7.2 = 11.1
  • The same applies to a gasoline engine that also has 200 HP: GPH = (200 x 0.5)/6.1 = 16.4

Step 3. Multiply the GPH by the fuel’s average cost to calculate how much you must spend for every hour of the trip. While doing so, factor in other points like cruising speed, the total traveling distance, etc. 

Suppose your gas engine of 200 HP burns about 16 to 17 gallons an hour in a 5-hour trip; you will need about 80 to 85 gallons for the trip. Let’s say the gas fuel price is $4.2 for each gallon; the total cost is around $336 to $357. 

Where Should You Fill Up Your Boat: Marina or Gas Station?

It’s recommended to fill up your boat at a marina or gas dock for more convenience and safety. But if you are on a budget, filling up your boat at a gas station can save you some bucks. 

Most docks and marinas charge you an extra $1 to $2 a gallon compared to gas stations due to taxes, transportation charges, etc. Plus, low-performance boats do not specifically require marine fuel; regular gasoline is enough to ensure their proper operation.

But, of course, there are still some exceptions. If that marina is near the ports, has shorter fuel transportation distances, or does not have to pay high taxes, their gas will likely be cheaper than gas stations located far away.  

Should You Top Off The Boat Tank of Gas?

It’s not advised to top off your boat tank as the gas will expand at higher temperatures when the engine is operating, heightening the risk of overfilling. Also, Ethanol in most gas types can absorb moisture from the air, which can sink to the bottom of the tank and wreak havoc on the engine. 

Some Tips to Save On Gas Costs for A Boat

Follow these simple tips to save money on your marine fuel:

  • Remember to always upgrade and tune up the gas engine
  • Avoid drag and idling
  • Reduce extra weight and excessive water
  • Consider increasing the speed with a motor sail
  • Do not travel in harsh weather conditions


When determining how much it costs to fill up a boat, numerous factors, including your cruising speed, boat types, gasoline choice, etc., are at play, so keep them all in mind. 

To optimize fuel consumption (and reduce the gas cost), remember to upgrade your boat often and avoid bringing it out in harsh weather. Write to us if you need help with anything!

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Alex Lewis

Alex Lewis

Petroleum Engineer At Rex Energy

I have worked in a variety of roles and professions, from quality engineering in the automotive industry to production engineer in the oil and gas sector. From a technical point of view, these roles have shown me how to design a process, ensure it is efficient and up to standard, and manage the execution of the said process from start to finish.

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