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.

Run time

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.

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.

  • Yes: 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.
  • No: All good, next test

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.

  • Yes: 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.
  • No: All good, next test

Gas

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.

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.

  • Yes: 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.
  • No: All good, next test

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.

  • Yes: All good, next test
  • No: 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.

Carburetor & oil pressure switch

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.

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.

  • Yes: All good, next test
  • No: 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.

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?

  • Yes: All good, next test
  • No: 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.

Fuel flow

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

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.

  • Yes: All good, next test
  • No: 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.

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.

  • Yes: All good, next test
  • No: 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.

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