Boat Engine Keeps Stalling: Here’s What To Do

One of the worst things that can happen to you when you are trying to spend a day on the water is having some engine problems. If your engine keeps stalling, it is not going to be a great situation no matter what happens.

Regardless of what size boat you are on, this is going to be a pretty big cause for concern. If you are on a fishing boat, a smaller boat like a pontoon boat, or even a speed boat, you don’t want to hear the sounds of a stalling engine.

That means you have an unreliable motor and that can leave you in an extremely dangerous position depending on where you are in relation to where you started.

You won’t be able to maneuver in a boat that doesn’t have a working engine, so this is a pretty serious topic. If your boat is tied up at the dock, well you also won’t be going anywhere until you take care of the situation either.

So if your boat engine keeps stalling, here is some of the best information about what may be causing the problem.

Why Do Boat Engines Stall?

You’ll need to figure out the cause of your boat engine’s failure.

A stalling boat engine is likely caused by:

Basically, you’re going to have to isolate the problem and try to figure out what is giving you this massive headache. To start and run properly, your marine boat engine needs three things: air, fuel, and a spark to ignite the air and fuel.

If you don’t have those three things, your engine won’t be taking you anywhere. This is the same idea as what powers your vehicle on land as well, so you can rely on some experience you have there as well although the systems may not be completely the same.

Many engines fail because the mixture of air and fuel is incorrect. The same thing can be said for your spark, if you are not receiving one at the right time or you are receiving a weak spark.

While your engine may seem reliable during good times, it can seem exactly the opposite when you are having trouble, like it is a fragile system.

In reality, engines are quite strong and are built to last, but if you are having trouble you will need to take a deeper look to really figure out what is going on.

Engine Problems

It is possible that you will see your problem coming with your boat engine, but it is just as likely that you won’t receive any warning from your system.

There are problems that can happen when you are only first starting as well as when your engine is running hot. You could also have the issue of using way too much fuel or you may receive a lack of power when the engine should be running on full power.

All of these kinds of problems can mean that you may want to take a look at your entire engine system if you start to experience them from time to time.

You should try to perform regular maintenance on your engine and check even more frequently if you feel like you are having any kind of performance issue to try and find a problem earlier rather than later.

Although no one likes to find out about bad news; performing regular maintenance on your engine will help you find problems when you can deal with them as opposed to when you are out on the water in your boat.

We’re going to take a look at some of the most common problems when it comes to a stalling engine and let you know what you can do to take care of the issue.

Bad Spark Plug

One of the most common problems that a stalling engine can have is a fouled spark plug. This basically means that some sort of substance is causing a problem with the way your spark plug normally works.

It could be fuel, dirt, or oil – it’s just any substance that could get onto the electrodes in your spark plug that would prevent the spark plug from producing a spark that is strong enough to ignite the air & fuel to actually start your engine.

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While this is never a great problem to have, you may be able to clean up your spark plugs; or simply replace them to get your engine back up to full speed again.

Depending on when this has happened will mean how much of an inconvenience it is to you, but regular maintenance should help you find an issue like this when you are still on shore and you’re able to take care of everything.

Bad Air Box

Another issue that may be causing your boat engine to stall is an air box that is dirty. This could also be known as a clogged flame arrestor. Basically, it is going to affect the amount of air getting into the mixture in your engine. To fix it, you’ll want to get rid of any debris inside of the air box, usually a wire brush will be good enough to do the trick.

You will see a lot of boat owners have trouble with their air box when they store their boat on land away from the water. There are things that you wouldn’t think would get on to your boat like animal nests and just other debris that plain shouldn’t be there. If you check this area before you use your boat; you should be able to combat the effects of an engine that is stalling due to poor air flow through the air box.

Stale Gasoline

Many boat owners find that their boat engines are stalling when they use their engine for the first time in a new season. While it might seem like bad luck, it may be related to the gas that you are using.

Gasoline can go bad after a period of a month or so; especially if it is mixed with ethanol which is the case in many areas.

If your gasoline is mixed with ethanol, it is more likely to attract moisture over time. That moisture is going to mix into the gasoline and will dilute the gas which will mess up your mixture and cause your engine to sound like it’s trying; but it just isn’t working out.

You definitely want to perform regular maintenance on your boat to make sure that you aren’t using old gas; however as long as there is no damage to the system then this can be a somewhat easy problem to solve.

Why Do Boat Engines Stall and What To Do About It! - Best Boat Report

Low Compression

If your boat has piston rings that get worn or it has old cylinders or leaking valves, you may end up with low compression in your motor.

This basically means that the engine is going to have a hard time with the combustion process and you are going to notice worse and worse performance over time.

This is one of the biggest reasons to always be checking your boat engine and to notice if the performance seems to be dropping because you should be able to catch this kind of problem before it becomes a completely non-working system.

Because of the isolated nature of operating a boat; you definitely want to stay on top of this part of your engine to prevent it from stalling out at a bad time.

Bad Airflow Sensor

One problem that more boats are having these days is a bad airflow sensor. This occurs when your boat motor is fuel injected; it occurs when you have a dirty or just plain not-working airflow sensor.

Fortunately, this one can be easy to fix because you may need to simply clean up the airflow sensor or have it replaced to get your boat engine performing at top levels again.

Dirty Carburetor

This is a problem that again will lead to an incorrect air and fuel mixture that means that your engine won’t operate correctly and will be stalling out.

This mixture is quite important so it matters to get it right, you may need to replace the carburetor.

Fuel Line Damage

Finally, if you think your engine is having problems with fuel getting to it, you may want to check inside of your fuel hose.

It’s one of the parts on your boat that can deteriorate over time, which will lead to a lot of stalling or even complete failure in your engine if you haven’t checked it and it has gone bad.


The first things you should look at trying when your boat engine keeps stalling are:

  • Replace your spark plug
  • Clean air box
  • Replace gas

If these easier fixes don’t work, you may want to try some mechanic work and check your:

  • Pistons & cylinders
  • Airflow sensor
  • Carburetor
  • Air control systems
  • Fuel Line