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How Long Can You Leave Gas In A Boat?

A boat gas terminal is shown in this file photo.

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Gas is yet another essential item in a boat. Gasoline is essential for any combustion engine, whether it’s an outboard or an inboard. So, how long can you leave gas in a boat?

Leaving gas in the boat can be dangerous. Luckily, there’s a specific time limit to which leaving gas in a boat is safe. Since it’s a flammable item, it becomes a significant responsibility of the owner to take extreme care of it.

 A boat filled with gasoline is no less than a live bomb when stored in a garage or other shelter. This section deals with everything related to boats and gas.

Practically, it is possible to leave gas in a boat. Not for too long, but leaving the gasoline in a boat is somewhat safe. However, in reality, people can’t empty the gas tank every time at the end of the boat trip. It’ll be frustrating to empty and then refill the gas before and after the boat trip if going semi-regularly.

If you are looking for some good knowledge of boats and gas, you’ve come to the right place. However, the main concepts we want to discuss are related to old gas. 


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Go through this article till the end to find out the essentials of the gas and boat information you NEED to know. Every section has its theme and set of information in the form of questions and answers, along with the supporting facts.

Can You Use Old Gas In A Boat?

Using old gas may seem to be a good habit. But, the question arises is whether it is feasible or not? Is it possible to use old gasoline in the boat? This section deals with all the facts and information related to the usage of old gas in the boat. 

In general, YES, one can use old gas in the boat. Using old gas is acceptable and possible, but with some conditions.

Using old gas with new fuel can save a lot of money, but it comes with a price. Due to the combination of old gas + new fuel, it degrades the combustibility. It severely affects the engine. As a result, one may experience sputtering or engine not starting.

A typical fuel conditioner is shown.
A typical fuel conditioner is shown.

Use a fuel conditioner to help with using older gas in your boat.

How To Use Old Gas In The Boat?

Never use pure old gas in the boat. It means that one should always mix old gas with some fresh gas. It won’t be just like new gas, and there might be some sputtering, but it will be better than what one will get by using pure old degraded gas alone.

Or better yet, don’t use the old gas but bring it to be disposed of at your local community recycling facility (call first to make sure they accept old fuel). Most municipalities have a disposal program for things like old paint, fuel, and other potentially harmful or dangerous liquids.


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When not to use old gas?

There can be times when the owner must not use old gas. But what makes the old gas unusable? Here’s the list:

  1. Gas with water. If there is a high content of water mixed in with the gas, then it cannot be enjoyable for your engine and should be avoided.
  2. If there are some dust particles, rust, dirt, or discoloration, then the gas is contaminated. Avoid using it.

Effects of using old gas

It’s a well-known fact that old gas is not at all good for the engine’s health. But, those who’re not aware of the severe effects of using old gas in the boat should be aware that damage to inner seals from dirty gas can occur, which will require an engine rebuild if bad. Here are a few points to keep in mind:

  • Always keep in mind that old gas = lousy gas. When this lousy gas fills the pipelines and reaches the engine, it can damage the engine severely.
  • The adverse effects of using bad gas are like a slow poison to the engine. The effects are not visible initially, but when the results start to appear, it’s already too late. There can even be damage to the pistons themselves, which can destroy an engine.
  • Cleaning the engine and other parts will be very costly. So, if one thinks that they can save a couple of bucks by going with the old gas, they may spend more on repairing damages.

But as stated before, it is safe to use old gas as there’s a time limit to that. Generally, observations show that old gas, which is not more than 90 days old, is safe. In other words, one can expect gas to be safe to use for up to 90 days. 

Without alcohol, this limit goes up to 6 months. However, there have been a few lucky owners who were able to use gasoline as old as one year.

To maintain your boat engine’s safety, it is strongly recommended not to use gas older than 50 days.

What can I do to increase the storage time?

If the safe storage time on an average is 50 days, as stated above, here comes another question. Is it possible to increase this storage time to save money? The answer is YES. It is possible to increase the storage time of the gasoline of the boat.

  • Using a fuel stabilizer that can increase the storage time of the gas in the boat can add months to its longevity.

Can I Leave Gas In My Boat Over Winter?

Leaving gas in the boat is again a significant concern. Many experts believe that it is safe to leave the gas. On the other hand, many believe that it is not at all safe to leave the gas. 


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This section revolves around leaving the gas in the boat, primarily through the winter. The idea is to provide relevant information related to leaving gas in the boat during the winter season.

The answer is YES. One can leave gas in the boat during winter. However, fuel treatments must be added to maintain gas quality.

  • Storing gas in the boat during winters is risky. There are some issues, which can damage the engine. We cover this below.
  • To ready the boat to sail in the next season, it is essential to take measures to keep the gas as it is till the end of the winter.
Fuel Stabilizer will help keep your boat fuel over the winter.
Fuel Stabilizer will help keep your boat fuel over the winter.

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Why Is It Not A Good Idea To Store Gas In The Boat During Summers?

Summers are scorching, and the gas is highly flammable. It is well-known that storing such an item is extremely dangerous. As the temperature of the atmosphere increases, it can cause a blast, hence not a good idea in the view of safety.

For your information, blasts in the boating industry due to fuel and gas, etc. are terrifying and dangerous and occur in an instant, often without warning. Such situations are tough to handle and can cause property damage, injury, and even death. 

What Can Happen If You Leave Gas In The Boat During Winters?

There is a possibility that ice will form inside the engine, and will block the entire pipeline. Such a situation will generate a considerable repair bill.

To overcome this issue, make sure that no ice forms in the engine. 


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For prevention, make some arrangements for heat, which is suitable for preventing ice formations. Ensure that the arranged heat is not too hot, as it can cause a blast in the boat. Using something along the lines of a block heater works well.

Never let water get inside the engine or tank. Not only ice, but one needs to keep the pipeline, tank, and engine away from water. 

A minute amount of water is acceptable because it’ll get burned during the combustion. But a vast amount of water will be a problem. Ethanol is said to absorb water, so it can deceivingly hide the amount of water in the gas. For this reason, alcohols are not recommended unless advised by the engine manufacturer.

Winters will cause gas to contract, changing the atmospheric pressure inside the tank. It can be a problem, so make sure that the gas tank is more than 50 percent filled.

So Is It Safe To Leave The Gas?

After analyzing the problems mentioned above and the solutions, if the owner feels confident, it is safe to leave the gas in the tank during winter. The best practice is the use of fuel additives that help maintain gas quality.

What Do You Do If Your Boat Runs Out Of Gas?

Running out of gas is a risky situation. It can be a significant issue if the boat is far away from human civilization. Panicking is not a solution. This section revolves around what one can do if your boat runs out of gas.

Even if the boat is out of gas, there’s nothing to worry about (unless you’re caught in a storm). There are some effective actions that one can take in such a situation. These include:


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  • First of all, set the anchor, so that the boat doesn’t float away to any other unwanted place.
  • Having a satellite phone is excellent. Quickly dial for the emergency helpline. According to data, most people stranded without gas have faced rescue in a relatively short time.
  • Use the boat parachute to sail with the wind force. This technique is proven to be effective. The use of wind force will let you sail in the direction of the wind. If the rider believes that the wind direction is favorable, then DO NOT WASTE even a single second. Because wind direction tends to change anytime, so don’t let the opportunity slip away.
  • Generally, there are many coast guards, and most people are lucky enough to encounter one in some time. But, don’t just sit back and hope for help to appear by luck.
  • Use oars (if any). It’ll be best to row by self, instead of staying in one place.

What Should One Do To Avoid Such A Situation?

There are several measures to prepare to avoid such a frustrating situation. After all, precaution is better than cure. These include:

  • Keeping a pair of oars is a wise idea. It is best because when the engine fails, only the manual system is left, and it comes in handy for small boats.
  • Keep a working satellite or radiophone handy.
  • If you don’t believe in emergency fuel, that’s proof of innocence and stupidity. Never see emergency fuel as a burden. One should always keep emergency fuel in the storage of the boat.
  • Other small emergency items include:

Running out of gas is a rare condition, and arises when the rider isn’t well prepared. It is straightforward to avoid it if one follows the guideline stated above.

A spare gas can is a good idea onboard.
A gas can will save the day if filled and stored as a backup onboard.

How Long Can Gas Sit Before It Goes Bad?

Gasoline in the boat will go bad after some time for sure. Many people have confusion regarding it’s life expectancy. 

This section is all about gas life, and how it is affected due to several phenomena.

In the most straightforward words, one can expect the gas to be good for up to 90 days. At maximum, this can go up to 120 days, given the appropriate conditions. But, gasoline can be suitable for up to 120 days only when:

  • It must be in a sealed metal or a plastic container.
  • It must not mix with water nor contain water in the gas.
  • No ice formed inside the container during its storage.
  • Ideally, the gas treated with a fuel additive is used.

What do you mean by bad gas?

Bad gas is a term used for gasoline that has lost or has reduced combustibility. But what causes this to happen?

The pure gas tends to lose its combustibility because of evaporation and oxidation. Such gas is said to last for only 50 to 90 days. In other words, the brand new sealed tank of gasoline can stay good for 120 days but used, or old gas has a life expectancy of about 90 days at most. 

How do you know that the gas is bad?

It is fine to expect gas to stay suitable for up to 90 days. But how will one tell or identify lousy gas? For this, follow one or more of these steps:

  1. Check for the foul smell (but avoid inhalation – it’s bad for you). If the smell is the same as that of a brand new and sealed one, then the gas is perfectly fine. Or else, there’s an issue. The gas that has a sour smell is bad.
  2. The appearance can also let one know about its health. A gas that is darker than usual is not good either.
  3. If one is experiencing issues in starting the boat engine, it is probably due to harmful gas. Low combustion is a symptom of bad gas. If the engine is not starting in one, two, or three goes, then check for deficient gas.
  4. Sometimes, check engine light may illuminate. It generally happens due to poor gas.

What can happen if you go out with bad gas?

Even if the boat has terrible gas, it may still make the boat run for some time. But that’s very risky. If the owner is aware of substandard gas in the engine and still sailing, that’s not a good idea. 


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Here’s what can happen if one still decides to ride with second-rate gas in the boat:

  1. Severe or permanent damage to the engine can occur.
  2. The engine may stop functioning suddenly. It may even die. If that happens, then all you can expect is an enormous repair or replacement bill.
  3. Inefficient engine performance.
  4. The output of the engine will degrade. A higher rate of gas consumption will occur, and still, it will result in low distance traveled.
  5. In the worst-case scenario, the boat may blast. And if the blast happens, that’ll be bad, which will be no less than an action movie scene.

It is strictly recommended not to go out on a marine trip with lousy gas.

So keep a spare gas tank with you, just in case.

A spare gas can is a good idea.
A spare gas can is a good idea.

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