Ethanol (E10) and boats don’t mix!

If you don’t want to read any more of this page, at least read this: DON’T USE E10 IN YOUR BOAT

While ethanol is ok in many, but not all modern cars, some boat owners are about to experience melted fuel tanks, leaks and damaged engines.  That’s why all of the four oil companies we called recommended that I didn’t use ethanol in any boat. 

In Qld and NSW, where there have been government imposed E10 mandates at times over the last few years, BP has a policy of putting a warning sign to boaties on its pumps.  Ethanol fuel is also being sold in other states.

David Heyes, of BRP Evinrude and Chairman of the Australian Marine Engine Council (AMEC) recently stated that his members were alarmed.  David explained that while almost all modern outboards will at least tolerate E10, the outboard industry was very concerned with the potential damage to fuel systems and especially for the safety of boat owners.   Older outboards are not designed with E10 in mind.

So while outboards can cope – there is no Boat building standard that requires hulls, fuel tanks, hoses and filters to withstand Ethanol.  And when these components get damaged dissolved compounds pass through filters, destroying engines.   

The risks for boat owners come from three key characteristics of ethanol.  It’s a powerful solvent, it doesn’t stay mixed with petrol, and it has a very short shelf life.

  • The solvent nature means that it dissolves some of the components of fibreglass fuel tanks, as well as many elastomer (rubber like) materials found in fuel systems. These pass in solution through the very best filters and end up forming destructive deposits inside marine engines.  Chemical attacks on tanks and hoses mean the inevitable leaks are a fire risk.  That means a fire risk or at best a powerful solvent attack to the bilge surfaces.
  • Fuel spills will “craze” gel coat finishes, strip paint and corrode aluminium.
  • Ethanol and petrol will separate under normal, moist boating conditions and that only concentrates the Ethanol so it can do more damage. (a process called Phase separation)
  • Ethanol has higher volatility than most elements of petrol, meaning it evaporates off first.  That means it may go “sour” in as little as 2 weeks in summer.

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