Winter Yacht Maintenance – Fuel Tanks

If you want a hassle free start to your sailing season, then it is essential to have a good winter yacht maintenance programme to keep your yacht in tip top condition over the winter.

This week we look at good practice layup for your yacht’s fuel tanks.

Eeek!…Which way to go? Full or Empty

There has long been debate when it comes to winterising your yacht, as to whether your fuel tanks should be left full or empty over the layup period, and how much fuel should be left in the tank.

Full or empty, condensation is your enemy and in winter with the great range of temperatures experienced between day and night this can lead to condensation forming very quickly inside your tanks.

Full tanks?
If you keep the tank full and thereby eliminate the air inside the tank then this will help reduce the amount of condensation that will develop your fuel tank.

Condensation can contribute to the problem of phase separation of your fuel. This is when the water separates and sinks to the bottom of the tank, where the fuel pickup is generally located, which then means that when you start the engine after layup, the water is then sucked through your engine, rather than fuel.

Condensation can also accelerate the problem known as diesel bug. It may also be worth adding biocide which will eradicate and prevent the build up of these organisms known as diesel bug.

One point to note is that it is never a good idea to plug up vents in your fuel tank – this can create unwanted pressure and cause leaks to your fuel system.

Empty tanks?
Some yacht owners would recommend emptying the tanks as there is a concern that fuel can go bad if left for a long period of time unused, and if old fuel is run around the engine after a period of inactivity, this can harm fuel injected engines.
However it is normal that marine diesel which has been treated will remain good for up to at least a year.

Emptying your fuel tanks and leaving them ventilated will essentially prevent condensation forming but for most owners it is easier to top up their tanks at the end of the season than figure out to pump out and consequently what to do with a few hundred litres of diesel.

Whichever route you take, then the main objective really is to prevent any condensation forming, so either filling them up or leaving them empty is always going to be a cause for debate!