Boat engine starts, runs a little then dies after a few seconds - Troubleshoot your engine

Here are 8 engine tests that will help you understand the cause behind your engine stopping right after starting. We also provide solutions & tutorials once the cause is identified. To keep the budget low, we start with the cheapest, easiest tests.

We wrote this because nobody wants their beautiful day on the water to be ruined by a malfunctioning engine, and whether you have a sailing boat, or a speed, pontoon, fishing boat, or personal watercraft, you want to be able to trust your boat motor.

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Run time tests

These tests are about how long your engine runs before it stops. This will help us understand why your boat motor is stalling. The length of time an engine runs after starting can indicate if the problem comes from the carburetor or the electrical system.
Test 
1

Does your engine run for a bit and then dies?

Once you start your engine, how long does it stay running before it shuts off by itself? If the engine stays running for a little bit after you release the key, this could indicate a carburetor issue.
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Yes

All good, next test
Your idle circuits could be clogged up. A dirty carburetor won’t be able to properly regulate the air and fuel mix inside the engine. This may cause your boat engine to stall.
Your idle circuits could be clogged up. A dirty carburetor won’t be able to properly regulate the air and fuel mix inside the engine. This may cause your boat engine to stall.
Need further testing
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No

All good, next test
Need further testing
Test 
2

Does your motor die as soon as the key is released?

When you try turning on the engine, does it die right after you release the key from the ignition? If so, this could indicate an electrical issue rather than a carburetor issue.
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Yes

All good, next test
The reason your engine is stalling could be electrical, because the key is supposed to activate the electrical system which helps turn on the engine.
The reason your engine is stalling could be electrical, because the key is supposed to activate the electrical system which helps turn on the engine.
Need further testing
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No

All good, next test
Need further testing

Gas tests

It is possible that your engine stops right after you start it because of issues related to the quality of the fuel that the engine receives. Let’s check that now.
Test 
3

Is the gas in your motor very old?

By very old, we don’t mean a couple months, we mean much more, like a couple seasons. Think back, when did you last fill up the tank? This could very much be the reason your boat engine starts then stops.
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Yes

All good, next test
Old gas can lose its capacity to burn. Therefore, old gas can create a situation where proper combustion inside the engine is prevented, and your engine stalls.
Old gas can lose its capacity to burn. Therefore, old gas can create a situation where proper combustion inside the engine is prevented, and your engine stalls.
Need further testing
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No

All good, next test
Need further testing
Test 
4

Is the fuel filter clean with no water or impurities?

To do this, you need to pour some gas that has been through the filter already into a clear container. Then inspect it for water or impurities, they could be the cause of your engine problems.
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Yes

All good, next test
Need further testing
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No

All good, next test
It can be pretty bad if something other than fuel is getting inside your engine. On top of preventing proper combustion, impurities could damage your engine.
It can be pretty bad if something other than fuel is getting inside your engine. On top of preventing proper combustion, impurities could damage your engine.
Need further testing

Carburetor & oil pressure switch tests

The role of a carburetor is to mix the right amount of fuel and air for combustion. If it's not doing its job, you prevent combustion and therefore the engine stops. The oil pressure switch is here to check if there is not enough oil in your engine. If it is defective, it could turn your engine off for no reason.
Test 
5

Is there gas in the carburetor or injector?

To check for that, first you need to remove the cover of the carburetor or injector, then look inside. If there is no fuel, you might be preventing your engine from firing.
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Yes

All good, next test
Need further testing
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No

All good, next test
You might have a fuel supply issue, meaning the gas from the tank is having trouble getting in the carburetor. These issues can come from different parts of your engine.
You might have a fuel supply issue, meaning the gas from the tank is having trouble getting in the carburetor. These issues can come from different parts of your engine.
Need further testing
Test 
6

Is the oil pressure switch working properly and the cables are not corroded?

To test this, remove the wires from the switch and jump them together. If the oil pressure switch is malfunctioning, this could be switching your engine off for no reason. Then, look for signs of corrosion on the cables, are they shiny?
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Yes

All good, next test
Need further testing
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No

All good, next test
You most likely have a poorly functioning oil pressure switch. It is telling the system that your oil is low when it is not, and automatically turning off your engine.
You most likely have a poorly functioning oil pressure switch. It is telling the system that your oil is low when it is not, and automatically turning off your engine.
Need further testing

Fuel flow tests

Testing fuel flow is important because it can tell you if your engine is not getting enough fuel, and therefore not firing properly.
Test 
7

Is your gas pump working properly, and is its pressure at the right level?

To check if your gas pump is working well, inspect the relay, fuse, fuse holder, and harness connector pins. For the fuel pressure, you should aim for something between 4 to 7 psi.
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Yes

All good, next test
Need further testing
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No

All good, next test
Your fuel pump is most likely not pushing the correct amount of fuel inside the carburetor/engine. As a result, your engine cannot stay running and stops.
Your fuel pump is most likely not pushing the correct amount of fuel inside the carburetor/engine. As a result, your engine cannot stay running and stops.
Need further testing
Test 
8

Is the inside of the fuel line clean?

Shine a light inside the tube while keeping it straight, or pass a sponge or cloth through the line thanks to a string. The inside of the fuel line is susceptible to deterioration, if you don't take care of it, it can cause stalling.
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Yes

All good, next test
Need further testing
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No

All good, next test
You are preventing the right amount of fuel from going into the engine. As a result, combustion cannot happen properly and your engine is stopping.
You are preventing the right amount of fuel from going into the engine. As a result, combustion cannot happen properly and your engine is stopping.
Need further testing

Top questions about engine dying right after starting

Why does my boat motor start then die after a few seconds?

The source of the issue can come from different parts of your engine. So, do the tests listed above and you will be able to know what is wrong with your engine. 

The first thing to look at is how long does your engine stay running before it stops. The answer to this could indicate an electrical issue. 

Then look at your gas quality and fuel filter. After that, we recommend checking the carburetor and the oil switch. Finally, take a look at your input flow.

The fuel in my gas tank is old, what should I do?

Sometimes, if your gas is too old, it won’t burn properly, which could be the reason why your engine stops right after starting. 

The solution here is simple, replace the old gasoline with fresh one and test turning your engine on again. If you don’t know how to drain your tank. Google “drain tank” + “your engine make, model”, this should help you find the right resource.

What to do if the fuel that has been through the filter contains debris?

This could mean that your filter is not working properly and is letting impurities through. The solution here is to replace the old filter with a new one, and try turning on your engine again. 

What is the normal fuel pressure?

For many engines, the normal fuel pressure is 4 to 7 psi. If you are not within that, your engine is not getting the right amount of fuel. Try to replace it or clean its wiring.

How do I clean a clogged fuel line?

Among other reasons, a clogged fuel line can happen because of the fat content present in the fuel. You are in a classic situation where your engine is not getting enough gas, and therefore, stopping. Clean it by passing a sponge or piece of cloth through it.