How To Tell If Boat Engine Is Flooded? With A Secret Fix & Causes

The boat engine flooding is a common cause of boat breakdowns, especially on cool or colder days when the engine needs more fuel to run smoothly until it’s warmed up. If your boat couldn’t start, this could be the problem. Read on to find out the symptoms of a flooded boat engine.

A strong smell of gasoline, wet spark plugs, and most importantly, if the boat doesn’t restart for the second time or won’t start at all are the signs of a flooded boat engine. And sometimes, even if the engine sounds different while cranking it up also could be a sign of a flooded boat engine.

The above symptoms will vary slightly depending on how badly the engine is flooding and why it’s flooding. (more on this later). Generally, engine flooding occurs while starting the boat engine, not often when an engine is running (but it can happen).

It’s quite often in boats with an (old) carburetor-style compression system. However, it rarely occurs (still it can occur) in boats with (modern) fuel injection style compression systems if the temperatures are normal. If it’s cold or very hot, it can happen, too.

Just In Case – If you don’t know what is flooded boat engine means.
If the boat engine’s combustion cylinder is filled with more gasoline than required, it is known as a flooded boat engine. A flooded engine has too much gasoline inside the combustion cylinder but not enough oxygen to burn all the gasoline.
As a result, the engine in this condition will not start until the excess gasoline has been cleared. It is also possible for an engine to stall from a running state due to this condition. But generally, flooding occurs while starting the engine, not when an engine is running.

That being said, we will now see the symptoms of a flooded boat engine.

Will A Flooded Boat Engine Fix Itself? The flooded boat engine can fix itself if you leave it idle for around 10-20 min or more for the gas inside the combustion cylinder to evaporate. If the spark plugs aren’t too badly fouled and the whole compression system isn’t bad, leaving it alone will fix the flooded boat engine problem itself.

What Are The Symptoms Of A Flooded Boat Engine?

You can tell if your boat’s engine flooded when you spot these signs: A strong smell of gasoline coming out (especially around the exhaust), wet spark plugs, and if the boat doesn’t restart for the second time or won’t start at all.

A Strom Smell Of Gasoline

The first thing you will want to look for is the smell of gasoline. For the most part, when an engine is operating properly, you should not be able to smell any gasoline on board (especially near the exhaust).
This is because when working correctly, the fuel system will deliver fuel into the engine at the exact rate that the motor burns the fuel. However, in a flooded engine, the fuel is coming out too fast and isn’t being burned.
As a result of the fuel not being burned, the gas builds (floods) up inside the combustion cylinder. So, it is common to smell gasoline when you try to start the boat, and it doesn’t start successfully.
Even if you see gas dripping from the engine, it could be due to flooding. So, if you begin to smell gas when starting up your boat, it could be a sign that your boat’s engine is flooded.

Wet Spark Plugs

If an engine becomes severely flooded, it may result in fouled spark plugs. A fouled spark plug is when the spark plug ends get wet due to an excessive amount of gasoline inside the combustion cylinders.
When a spark plug is wet, the electrical energy that tries to fire during starting, stops out instead of firing. If discovered in time, fouled spark plugs can sometimes be cleaned, but more often than not, they should be replaced.

Related Post – How Often To Replace Boat Spark Plugs? Check this article to know more about when to replace the spark plugs, simply avoiding some serious problems with too old spark plugs.

Trouble “Restarting” The Boat/Won’t Start At All

If you start up your boat and then shut it off shortly after, when it’s time to start it back up again, you might notice that it will have more difficulty starting up your boat for the second time around.
A boat engine that has this kind of problem likely has a flooded engine. Sometimes, to help a vessel start, a boat will send some extra fuel to the engine to help it get started.
However, if the boat isn’t allowed to run long enough to burn the extra fuel, the fuel doesn’t get burned off and will remain in the engine. As a result, the fuel mixture is too rich when you try to restart the vessel.

Sometimes, the boat might not start at all. Now, there are many things to check like starter, battery, fuel pump, fuel filter, and spark plugs. Click on those links to see all the articles we have written on those and how to look for their bad signs and some easy fixes to improve their lives.

Related post – Boat Won’t Start And Just Clicks? Check this article to know why sometimes you hear a clicking noise while starting the boat and some easy ways to troubleshoot it.

How To Prevent Boat Engine From Flooding? Unnecessarily opening the choke for longer periods and regular inspection of the whole compression system will prevent the boat engine from flooding.

What Are The Causes Of A Flooded Boat Engine?

The Boat engine flooding can be caused either due to bad spark plugs that are unable to ignite the air-fuel mixture properly, a faulty cylinder compression system, or leaving the choke open for a long time. Any among them will increase the fuel ratio inside the cylinder, flooding the engine.

What Happens When Boat Engine Floods? When a boat engine floods, it will not start the boat engine, or if the engine floods while you are running in the lake, the boat bogs down until it stops. Unless if you remove the excessive gasoline inside the combustion cylinder, the boat will not start.

Bad Spark plugs

If the spark plugs are worn out or damaged, they won’t produce a compelling instantaneous spark. This will then lead to a flooded engine as the air-fuel mixture won’t be ignited properly or at all.
Failing spark plugs can also cause the boat engine to misfire and thus affect its performance. For example, a single spark plug that fails to ignite the fuel-air mixture can cause a halt in the running of the engine.

Faulty Fuel Injection System

There could be a possibility that the whole fuel injection system could be damaged. This is because fuel injectors are in charge of injecting fuel under high pressure into the combustion chamber.
If injectors are faulty or stick open, or there is high fuel pressure, then the engine will flood. The fuel pressure that normally remains in the system can drain out through the injectors and cause engine flooding conditions.
However, it rarely occurs in boats with (modern) fuel injection systems if the temperatures are normal. If it’s cold or very hot, it can happen, too. But it is common in (old) carburetor-style boat engines.

Related Post – What Are The Signs Of Old (Bad) Gas In A Boat? Check this article to know more about how the old or bad gas struggles the boat while starting the engine and how to deal with it.

Faulty Carburetor Or Carburetor’s Needle Valve (In Old ones)

The carburetor is an old-school device (but still used in many boat engines) that mixes air and fuel to produce the proper mixture for the inner combustion engine. If the carburetor is faulty (weak or damaged nozzles, damaged gaskets, a punctured float, or else), it can easily cause a very rich mixture and a flooded engine.
This couldn’t entirely be a faulty carburetor; it could be the needle valves. Carburetors installed on your engine use needle valves. The needle seat valve controls all of the fuel flow into your carburetor. So if it is faulty, it will send more fuel inside the combustion chamber.
And if the whole carburetor is faulty (weak or damaged nozzles, damaged gaskets, a punctured float, or else), it can easily cause a very rich mixture of fuel inside the boat engine, flooding the boat engine.

Leaving The Choke ON For Long Periods

Leaving the choke on could be one of the common problems that cause the boat engine with a carburetor combustion style system to flood. A choke valve/cable is designed to restrict airflow in the carburetor of an engine, thereby increasing the fuel flow.
This could really be beneficial if your boat engine is stuttering and won’t seem to start, you can turn on the choke to give it a boost of fuel, which is oftentimes enough to make it turn.
However, if you leave the choke on for longer periods before the engine is turned on, it can immediately result in flooding, as too much fuel is pumped into the cylinders. So, don’t apply the choke unless it is the first start sequence of the day or it doesn’t start.

How To Fix (Start) Flooded Boat Engine?

To start the flooded boat engine, wide open the throttle (with no choke) and wait for a couple of seconds to send air inside the cylinder to compensate for the excessive gasoline present inside the flooded combustion cylinder and then try to start the boat engine.

A flooded boat engine will have too much gasoline and not enough oxygen (air). So by throttling all the way down, you will send more air inside the cylinder, which basically flushes the extra fuel away, clearing the plugs allowing them to spark again and start the engine.

If the plugs are soaking wet, you can dry them first (with compressed air or laid out in the hot sun) to assist in starting. If this doesn’t crank up the boat, there may be other problems within your boat engine preventing your boat engine from properly starting.

Related Posts – Now, there are many things to check like: starter, battery, fuel pump, fuel filter, and spark plugs. Click on those links to see all the articles we have written on those and how to look for their bad signs and some easy fixes to improve their lives.

How Long Does A Flooded Boat Engine Take To Clear? On average, 10 – 20 minutes wait time is sufficient to clear the gasoline inside the flooded boat engine. However, depending on the severity of the problem, sometimes you may need to wait for 30 minutes or more before cranking up the boat engine.