3 Symptoms to Detect a Dirty Flame Arrestor – How to Clean?

As much as the flame arrestor on the outboard can prevent explosion, it can cause surge or engine blow-up due to dirt. So, you should look for the dirty flame arrestor symptoms that will help you know when to clean it and save the boat from burning down its engine!

Indeed, there are three major symptoms that signal the arrestor is clogged. The engine won’t run at its highest power, and the acceleration will be too slow to ride.  Also, the RPM rates of the boat will fluctuate.

In case you don’t know how to clean such a device to protect the engine, we’ll help you out with the process, including the maintenance tips too. Stay tuned!

How Do You Know If Your Boat Flame Arrestor Is Dirty?

As a boat flame arrestor assists in transferring gas and liquid to keep the engine functioning properly, a dirty arrestor affects the motor or engine. 

Consequently, you’ll notice performance reduction or other unit issues related to the engine. And here are some detailed dirty flame arrestor symptoms –

Symptom 01: Lack of Engine Power

Debris or piled-up dirt in the arrestor eventually blocks its fuel pumps and carburetor. And these clogged units fail to regulate the proper liquid and fuel mixture required for the engine to function without any stalling. 

Thereby, the engine loses power and fails to run correctly. For this reason, you will have a hard time moving the boat ahead in water and turning without the engine operating at its full strength!

Symptom 02: Slow Acceleration

Bad or clogged fuel systems due to dirty pipes or units of the flame trap prevent the boat from accelerating at a proper rate. Because the engine doesn’t get enough fuel-air proportion to accelerate hard. 

Basically, you’ll notice a delay in power or a surge. It may lead to seaweed, rope, and fishing lines entangling the blades and this debris prevent the outboard from running at full acceleration. 

Although the engine sounds okay, the speedometer shows the boat is slow. Clear further doubts through the video clip: 

Symptom 03. RPM Rates Fall

According to Boating Magazine, a typical boat’s ideal RPM should reach around 3200 to 3400. But due to clogged or dirty arrestors, the engine can’t exhaust the gas to rev at a higher RPM. 

So, even if you press the throttle controls, the boat won’t increase its speed. We’d suggest you tap the flame arrestor or engine gently. 

And if there is a rattling sound, chances are there is dirt and debris in those units. With a clogged fuel filter of the flame trap device or arrestor, it can’t strain the debris and prevent them from reaching the engine. 

A dirty engine and flame trap block the inlet while throttling up. Therefore, the outboard bogs down, and the RPM rates fall, which leads to slow speed during a ride.

Can a Faulty Flame Arrestor Screen Lead to a Throttle Issue?

If the flame arrestor is dirty, its housing mouth opens wide while riding the boat. And with this wide unit, the engine gets more air, which restricts the throttle settings to control the boat. 

For example, even if you try to slow down the speed during a turn, the throttle won’t be able to control the trim. As a result, the boat tends to lean sideward! 

Moreover, the dirt from the arrestor slowly blocks the attached carburetor and fuel pumps with debris. And eventually, these specks of dirt go into the boat engine, which leads to an air leak in the fuel lines. 

And due to the pressure of the leak, the RPM fluctuates even at a specific throttling setting that restricts the speed of the boat. So, throttle controls don’t work properly due to faulty arrestors. 

How to Clean Boat Flame Arrestor?

Without cleaning the dirty flame arrestor, you can’t expect to accelerate hard and experience a smooth ride without stalling. So, follow these steps to clean the unit and keep it functioning – 

Step-1: Detach the Parts

First, take a photo of the installed arrestor to note down the installation position. It will help you attach the cleaned device without damaging any other parts. 

Then, disconnect the arrestor from the carburetor and detach any removable parts. With a soft bristle brush, ensure to remove the dirt or debris, and wipe it off with a clean cloth.

Step-2: Coat and Wait

From a local store, get the carburetor cleaner and go through its direction of use. Dilute the solution as per the manufacturer’s guidelines. Afterward, you can apply it to the clogged flame trap and let it soak so that the debris can loosen up. 

Or else, you’ll need to scrub with force to remove the dirt. Keep the unit away from flammable objects while it absorbs the mix. 

Step-3: Scrub and Wash

Once the flame device soaks the liquid, wash down the dislodged contaminants by taking assistance from a garden sprayer or hose. 

Then, gently scrub the outside of the unit and rinse it off. Let it dry before installing it to prevent engine failure due to water drops. 

After it dries, attach it and check whether the engine and RPM are at full power or not. If yes, you’re all set to ride a long distance!

Tips for Maintaining the Flame Arrestor to Prevent Getting Dirty

Sometimes, dirt-filled flame arrestors can become way too damaged beyond repair. And even cleaning can’t fix it! So, in order to prevent such scenarios, keep it clean on a regular basis with the maintenance guide: 

  • After every ride, inspect the carburetor along with the flame device. If you find any weeds or trash inside out, remove them immediately. 
  • To prevent corrosion or rust build-up, lubricate the movable parts so that the rust does not spread throughout the flame device.
  • Check for any oil leakage in the device. If it drips off oil, clean it after every ride.
  • If the housing mouth of the flame trap unit or arrestor seems wide open, try to dry off any water in it. And then install it properly to block the dirt from getting in. 

Frequently Asked Questions

The flame sensor or arrestor of an outboard is a tricky device to deal with, especially when it builds up debris. So, if you’ve any further doubts about it, feel free to check out these answers:

Can You Clean the Dirty Boat Flame Arrestor With Soap Water?

Yes, you can do so. But the solution won’t be effective in removing rust or debris that has been piling up for a long time. Only the carburetor cleaner can strip off the grease inside out.

Is It Safe to Go To A Ride With A Clogged Flame Arrestor?

No, you should avoid starting the engine or going for a long ride at full speed. Although it may function for a while, the engine won’t be able to exhaust the gas eventually. Furthermore, it’ll explode once it backfires!

How Often Should You Clean the Flame Arrestor on a Boat?

It depends on whether the arrestor is new or not. If new, you can clean it once a year. If it is several years old, try to detach and wash it after every ride. Avoid over-cleaning the device to increase its lifespan. 

Why The Flame Arrestor Is Installed on Top of the Engine?

The arrestor mounted on the engine keeps the flame produced by the engine backfires from entering its housing.  And it also blocks the flame from getting into the engine. Therefore, to prevent an explosion, this placement is essential. 


Generally, users notice the dirty flame arrestor symptoms while riding the boat at its full speed and controlling it with the throttle controls. We’d advise you not to go for a long ride with such a clogged unit. 

Because in that case, it’ll be hard for you to come back to the shore without a functioning engine. And the worst thing is that it may explode! If you aren’t used to detaching or handling the arrestor parts and cleaning them, better you contact professionals too. 

Although they will be expensive, it’s ideal to keep the sensor from malfunctioning. And they won’t misplace their installation location.

Similar Posts