Using Fuel Stabiliser when Storing your Boat


The fuel in your boat can begin breaking down in as little as 30 days if it’s not being used, leading to corrosion and gum build-up in the system that can lead to starting problems, reduced engine life and poor running performance. With this in mind, it’s important to understand what to do when it’s time to put the boat away for winter.

Deterioration of Fuel

All fuel, whether it's petrol, diesel, biodiesel, E10 or E15, deteriorates with time. Fuel's deterioration rate accelerates when exposed to water, oxygen, light or heat and unfortunately marine fuel is at risk of all four elements that result in the fuel molecules being unstable.

E10 is a blended ethanol fuel with the fuel component reduced to around 90%. Phase separation can occur quickly in E10 when the fuel is left idle and moisture enters the system. The ethanol and unleaded petrol separate and cannot be blended back together. E10 tends to deteriorate quicker than other fuels and some would say that it needs to be drained and replaced after winter, even using fuel stabilisers.

Don’t Drain Fuel Tanks

Some people believe it’s best to drain the fuel from tanks before storing however that comes with a range of problems including:

  1. Disposal of fuel - you won’t be able to dispose of the fuel on your property so it will need to be dropped off somewhere authorised by your local council (i.e. tip, fire department, marina collection point) or stored in the shed which can create a potential hazard.
  2. Empty tanks attract moisture – with no fuel in the tank, moisture builds up causing corrosion and rust on the inside that you can’t see.
  3. Damage to the lines – it is impossible to completely drain fuel from the system so small amounts of fuel left in the lines will cause damage.
  4. Gaskets and seals can dry out – once dried out they are likely to crack causing leaks when you refill the tank.

Winterise your Boat

If you aren’t going to use your boat for several months while the weather is less than ideal, you need to winterise your boat. The winterising process is different for inboard and outboard motors. Consult your boat manual for instructions on winterising your boat or take it to your dealer.

Inboard Engines

Change the oil after running the motor to warm the oil a little so you can drain as much as possible. Remember to supply cooling water to the engine through the flushing port. Change the oil filter and then refill to the level while checking for leaks. Change the fluid in the transmission then remove spark plugs and spray grease into each cylinder. Wipe down the engine using a towel sprayed with fogging oil.

Fill the tanks with fuel and add in the correct dose of fuel stabiliser. Run the engine for several minutes to circulate the stabiliser throughout the system then remove the fuel line and wait until the engine dies to burn off fuel in the carburettors.

Outboard Engines

Run the motor to warm the oil then turn off the motor and tilt the engine up halfway, so the oil goes into the crankcase then drain. Change the oil filter and then refill to the level checking for leaks.  

Fill the tanks with fuel and add in the correct dose of fuel stabiliser. Apply the flush muffs or use the port to flush the engine with fresh water. Remove the cowl and with the engine running, grease the air intake at the front of the engine. Check the fuel lines, hoses and primer bulbs that are exposed to the sun and replace if they are showing any sign of wear. Fuel filters stop water getting into the engine and fuel tank so make sure they are clean and replaced every six months depending on the number of hours you’ve used the boat this season.

With the engine running, remove the fuel line and wait until the engine dies to burn off fuel in the carburettors to prevent deposits left from evaporated fuel.

Apply Bel-Ray Rust Preventative Coating to the propeller shaft and threads then change the oil in the lower unit. Finally, wash the engine down with soap and water and rinse off thoroughly.


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Fuel Stabilising Solution

The best option for safely storing your boat is to use a fuel stabiliser solution. Fill your tank with fresh fuel to about 95% and add a fuel stabiliser. It’s important that you use fresh fuel because no amount of stabiliser can take bad, dark or phase-separated ethanol and put it back together. Fuel stabilisers are preventative measures so only use it when the fuel is at its peak quality.

Sta-Bil Fuel Stabiliser will keep the fuel fresh for up to 24 months. The bottle comes with an easy to use measuring tool, so you don’t need a separate funnel or cup. Just tip the measured amount in the neck of the bottle into your fuel tank. Run your engine for several minutes after adding stabiliser, so the entire fuel system is treated and not just the fuel tank.

Benefits of Using Sta-Bil

Here are a few reasons why Sta-Bil is the top-rated fuel stabiliser.

  1. Selling for over 40 years – the product has been sold in the USA for 40 years and is now recommended by more than 100 engine and equipment manufacturers.
  2. All equipment – not only can Sta-Bil be used for winterising your boat, it can also be used in all petrol powered equipment you don’t intend to use for a month or more.
  3. Save costly engine repairs – Sta-Bil offers protection for your tank and the whole fuel systems including injectors and carburetors.
  4. Treat Rates – the smallest 118ml bottle of Sta-bil Fuel Stabiliser treats 38 litres of fuel, the 236 ml bottle is enough for 76 litres of fuel, the 473 ml bottle will treat 150 litres of fuel. The Sta-Bil Marine Fuel Stabiliser, that is specifically engineered for the marine environment, is more than four times as powerful and can treat up to 300 litres of fuel with only a 236ml bottle.
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The longer you intend to store your boat, the higher the dose of stabiliser you’ll need. If you are going to store for up to 24 months, you will need to use 60 ml for every 9.5 litres of fresh fuel.

A little time and effort spent on your boat before storing can save you on costly engine or fuel tank repairs and an easier start to the boating season.

If you have any queries about winterising your boat <link> or using fuel stabiliser, call Boat Accessories Australia on 1300 308 161 or send us an email.  

Category: Maintenance

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Thankfully, our Australian winters are not as extreme as our fellow boaters’ overseas who often face sub zero temperatures. Nevertheless, there are steps that need to be taken to ensure you’ll be ready to hit the water again once spring arrives.