How To Detect Fuel Leaks On Boats? (Explained)

Whether you are using gasoline or diesel, fuel leaks on boats can be the source of a major catastrophe.

In this article, we take a look at how to detect fuel leaks on boats and how to deal with them:

What Signs Should You Look for to Catch Fuel Leaks?

The first sign to look out to catch fuel leaks on a boat is the smell of fuel when you open up your boat.

Likewise, it’s usually fairly straightforward to identify a fuel leak on a boat; open up the bilge and see if there is any fuel floating around down there.

The bilge is the lowest point in your boat. So if you do have a fuel leak, this is where the leaked fuel will collect.

What Are the Symptoms of a Bad Fuel Line?

The symptoms of a bad fuel line are usually fairly obvious and can include the following:

1. A Slight Smell of Fuel:

One of the first symptoms of a possible issue with a bad fuel line is when you start noticing a slight smell of fuel coming from your boat.

Over time fuel lines or hoses will start to decay, and then they will begin to leak fuel vapors.

While you may not be too concerned at the time, tiny pinpoints or leaks that emit fuel vapors will start to produce a faint or sometimes strong odor of gasoline or diesel.

At some point, small leaks such as these will progress into larger leaks, and these will eventually cause more serious issues.

2. The Engine is Hard to Start, Misfires or Drops RPMs:

Another common symptom of a bad fuel line is engine performance issues.

If your boat’s fuel line develops any leak, then your boat’s engine performance will be compromised.

A bad fuel line will cause your boat’s engine to experience problems.

These problems can include symptoms like being difficult to start, often stalling, causing a drop in revs or RPMs, and can even stop the engine from running at all.

3. Actual Fuel Leaks:

The most serious symptom of a bad fuel line is when you have actual leaks or visible fuel in your bilge.

Any fuel line will eventually wear out or break down and cause issues.

Having a proactive maintenance program can help you to avoid these problems.

Also, any suspected fuel leak should be attended to as quickly as possible to prevent a more serious problem or safety hazard.

How Should you React if You Detect a Fuel Leak?

If you are on board your boat and detect a fuel leak, here are 5 easy steps you can perform to reduce any risks:

Act fast:

If you arrive at your boat and detect a fuel leak, you must remain calm but act fast.

Being proactive can help prevent fuel spills and any possible damage to the environment.

Plus, you will want to avoid the fine that this may entail!

Open All Hatches:

Opening all your hatches will create airflow, which is important for dispersing any build-up of fumes.

Fewer fumes equal less chance of a fire starting from any ignition points.

These ‘ignition points’ could be as simple as turning on the engine or even turning on a light!

Turn Off the Fuel Valves:

Unless the problem is the fuel tank, turning off the fuel valve will help stem fuel flow.

This will also help to isolate the problem.

If you still have a fuel leak after turning off the fuel valve, it is most likely that the fuel tank is the source of the problem.

Don’t Smoke:

Gasoline vaporizes at a much lower temperature than diesel, which means gasoline will ignite faster.

However, you still don’t want to take the risk of your boat bursting into flames, whether you use diesel or gasoline.

Avoid lighting matches or lighters and smoking anywhere near a fuel leak.

Try to Contain the Spill:

It is illegal to dump fuel, oil, or any other contaminants into the sea, marinas, rivers, or any waterways.

So, as tempting as it may be, don’t use your bilge pump to empty your bilge if it contains fuel.

Likewise, if your boat is on a trailer, don’t dump the fuel onto the ground.

To clean up the fuel leak, try to use absorbent pads or even kitchen paper towels to soak up the fuel. Then you can carry them in buckets or even plastic bin liners to a specialized hazardous-waste disposal site.

Your marina or club should be able to direct you to the nearest one if they do not have facilities on site.

Can You Always Smell Fuel Leaks on Boats?

You can always smell fuel leaks on a boat.

However, there could be several different reasons you can smell fuel on a boat, and there is a slim chance it may not be down to a fuel leak.

Perhaps you have accidentally overfilled the tanks, or it could be coming from an old-style fuel tank breather.

But even if you have no visible signs of a fuel leak in or around your boat, always check the engine and the bilge for any signs of a leak, and follow our tips above.

Are Fuel Leaks Typically Expensive to Fix?

This will depend on how ‘hands-on’ you are and what type of fuel leak you have!

We had an annoying small leak on our boat that took us about 2 weeks to trace and fix.

We replaced fuel filters, checked our fuel lines, and even had paper towels around our aluminum tank and under the engine to trace the leak. Eventually, we found a small crack in the fuel pipe connected to one of the fuel filters.

It was so small that you struggled to see it, but it emitted a slow drip when the system was under pressure. If we had called in an expert, it would have cost us a lot of money to trace and fix the problem, especially something small!

If you can find the leak yourself, it may be something as simple as replacing the fuel hose or even a hose clamp. However, if your fuel leak relates to your actual fuel tank, you will not be so lucky.

From a safety point of view, fuel tank repairs are not advisable, especially if you are going offshore or even deep-sea fishing in local waters.

How Often Should you Replace the fuel Tank on a Boat?

Fortunately, this is not an issue that most boat owners will experience unless you own the same boat for a very long time or if you are considering buying an older boat.

Most fuel tanks should last for 12-15 years if they are properly installed and maintained.

Obviously, the materials used, such as steel, aluminum, fiberglass, or plastic, will also play a part, but other factors like moisture and humidity come into play.

If your fuel tank is well ventilated and cleaned often, the life expectancy of your tank can indeed exceed 15 years.

Final Thoughts

When it comes to boat fuel tanks and fuel systems, you don’t want to take any chances to detect a leak.

Not only is gasoline or diesel a flammable material, but you also need to do regular maintenance to reduce the likelihood of your boat motor not starting or running correctly.

When it comes to safety on the water, you don’t want to take any chances with your fuel system.


Beware the Perils of Petrol

USCG Boatbuilder’s Handbook – Fuel systems

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