The most modern petrol engines in pleasure craft can run on SP95-E10, a blend of 90% petrol and 10% ethanol. Engine manufacturers assure us that the seals, tubes and other ducts in their engines are able to withstand this corrosive co-fuel. Engines, OK, but what about the peripherals?

But ethanol is an alcohol which, while not harmful or corrosive to engines, radically transforms a substance widely used on board pleasure craft: PVC in all its forms, which is used in the composition of sheaths, tubes and insulation, such as that used in some electrical cable sheaths.

When you consult the material compatibility guides, you read that PVC is resistant to ethanol. It is resistant, yes, but it also changes. This is the subject of numerous studies that conclude that PVC membranes exposed to solutions containing ethanol lose their plasticity.

What does this have to do with the subjects we're interested in?

Quite simply, PVC is present in virtually all electrical cable sheaths. But how can these sheaths come into contact with fuel? Fuel tubes can be slightly porous, fuel can spill out and slight leaks can occur.

On this RIB we have seen, the fuel supply tube runs in the same sheath as the engine power cables, the sensors and the engine wiring harness. The sheaths for all the electrical cables have changed texture. Sticky and deformed, they no longer fulfil their protective role. The fuel has deformed them to the point where the sheaths have separated from the cables.

The images show the sheaths deformed, but not damaged, and still playing their role of protection against chafing. But what would have happened if fuel had come into direct contact with a short-circuited cable?

Boom!

And how would an expert judge the condition of a harness like the one shown in this article? Defective, without a doubt.

Ethanol fuels already don't have many fans in the leisure boating sector, so I'm afraid this kind of consequence won't make them any more popular...