The Tohatsu manual says that the motor can use fuel with up to 10% added alcohol. Bio-ethanol (similar to what I use in my spirit stove) is being added to petrol in increasing amounts because it is considered a renewable resource. Some fuels have, or will have very soon, 15% added alcohol. Apparently this is OK for cars which get refuelled often, but bad if it sits around in a boat fuel tank for an extended period absorbing moisture in which case the water/alcohol mixture may separate out. How serious the problem is depends on who you ask.

The use of alcohol is an EU directive, so it is not surprising that the French company Total was one that continued supplying alcohol free fuel. Not wishing to compromise reliability I thought I'd buy my fuel from them but it turns out they have recently sold their retail outlets (in this area, at least, to Shell). Some brands of super-unleaded fuel have a lower alcohol content. Alternatively fuel additives exist to combat the problem - one is sold by Johnson/Evinrude.