Here’s another problem with biofuels
I have just found a surprising problem associated with biofuel petrol that contains alcohol. When used in outboard engines it causes corrosion, especially if fuel is left in the tank for a while. Apparently the alcohol evaporates and deposits its water content on the metal part of the fuel tank lid. The lid corrodes, bits of corroded metal drop into the fuel and bung up filters, or worse still the alcohol-petrol mixture softens the filters that are supposed to protect the jets. Some corrosion particles are large enough to jam open a needle valve. Since the particles contain metal they are quite difficult to dislodge.
I have bought a new lid but when I tested the metal part with a magnet it was revealed as mild steel, not stainless, so I expect a similar problem with the new lid. Manufacturers must know of the problem. Using stainless would solve it outright.
What can be done about it? Either avoid biofuel petrol, or keep the engine tank full to the brim. Always switch off the fuel and run the carburettor dry to stop the engine, and drain the fuel tank before storing the engine for any significant length of time. Quite a bore if you want to save a few pence per litre on fuel prices.