Water in the fuel – what to do?

Vatten i bränslet – vad göra?

💧 Water in the fuel – what to do?

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Water in the fuel is a very common problem in boats – and one of the biggest reasons for the engine losing power or stopping completely.


⚠️ Symptoms of water in the fuel

  • Engine sputters or dies when accelerating
  • Hard to start
  • Uneven running
  • Sudden loss of power
  • Sometimes white smoke

🔍 Why do you get water in the fuel?

  • Condensation in the tank (temperature differences)
  • Bad or old gasoline/diesel
  • Leaky tank or cap
  • Moisture from the surroundings

🔧 What to do immediately?

1. Drain the fuel system

  • Empty the tank completely if possible
  • Suck out the bottom → where the water collects

2. Change the fuel filter

  • Especially important if you have a water separator
  • Inexpensive but often solves the problem immediately

3. Refill with new fuel

  • Use fresh gasoline/diesel
  • Avoid mixing with old fuel

4. Check hoses & connections

  • Look for cracks or leaks
  • Tighten connections

🧪 Additional solution (quick fix)

  • Add fuel additive that binds water
  • Can help if the amount of water is small

👉 But: it doesn't work if there's a lot of water – then you need to drain the system.


🛡️ How to prevent the problem

  • Fill the tank full → reduces condensation
  • Use a water separator
  • Don't run on old fuel
  • Store the boat dry
  • Service the engine regularly

💡 Pro tips

  • Install a transparent fuel filter → you'll see immediately if there's water
  • Empty the separator occasionally (many forget this!)
  • Problems often arise after winter