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It’s All About the Facts: Why You Should Use E10 in Marine Engines

April 1, 2016


By Bobby Likis, President and CEO of Car Clinic SeaTechMarine states:   While most of our customers are aware of the problems that ethanol-based fuels can cause in their valuable boats, we've noticed that a number of people who do their own engine maintenance often don't realise that they could be doing significant, avoidable damage to their engines every single time they take them out. It's all about the valves During the combustion cycle in an engine, valves need to open to let in air or release gases, and then close again, creating a seal.  Problems with an engine's valves quickly lead to problems with the whole engine –the engine loses compression and runs poorly, stalls, and won't start reliably.  

Is It All about The Valves?

  • No not really! It – meaning engine performance and reliability – is more about performing routine maintenance services (as strongly pointed out on this company's SeaTech Maintenance site) and following proper servicing guidelines that include quarterly fuel inspections than it is ethanol blended fuel.
  • Engines that run poorly or won't start reliably and stall out may have entirely different problems than valves. Weak or bad ignition coils, worn & wide-gapped carbon-fouled spark plugs, worn out rings, poorly insulated plug wires and low battery voltage are but a few items that affect engine power and reliability.  To place the blame on ethanol-blended fuel for bad valves smacks of providing an easy target for some - not all - boat mechanics who would rather spread Myths than to learn the facts about fuels.
  • Fact is all engines wear, especially those running higher RPMs and under heavy loads as boats do... also clearly stated by SeaTechMarine.
  • What's missing in this article is the fact that valve seat (sealing) damage to car engines was caused by the removal of Tetraethyl lead (TEL), an organometallic compound containing toxic metal lead that for much of the 20th century was the chief antiknock agent for automotive gasoline. Not the addition of ethanol.
  • During the mid 70's, "leaded gasoline" was phased out, first in the United States and then in Europe and around the world because lead contributed to human lead poisoning as well as interfering with pollution-control devices installed in automobiles. Carmakers redesigned their engines for unleaded gasoline (in part) by replacing old technology valve seats with Stellite units.  In deed, the Automotive Industry has been updating its fleet for years and today delivers more HP and Torque with fewer emissions from smaller downsized higher compression turbocharged engines... all enabled by ethanol's high octane & cleaner burning properties.
  • It's self-serving that this article states that ethanol blends are OK for cars, but not boats. It's simply not possible (for me) to believe that the marine industry is still using engine-building technologies and materials from the seventies.
  • As for ethanol fuel damaging boat motors under loads and high RPMs, NBRA members race boats using ultra-high ethanol blended fuels. Click Vernon Barfield for proof.
  To that end, Mercury Marine states... - Ethanol E10 may be unfairly blamed for issues not related to ethanol use Identified need for a source of truth in the market - Certain companies are rather far-reaching in claims being made; creating consumer confusion/frustration
  • Some additive products may actually be doing more harm than good
Core technical issues - Control fuel quality for a certain period of time - Deposit and varnish control within fuel system - Automotive fuel is not designed for infrequent engine use (degradation issue) - E0 to E10 transition; real concerns, simple solutions A bottle of X will never solve 100% of the issues - Keep tanks clean, check filters, buy from trusted fuel sources - Be sure to keep up-to-date with OEM service intervals and protocol Buyer beware – resist the Myths - #1 priority of all OEM's is to ensure engine integrity, not sell a bottle of fluid
  • With so many cure-alls, voices, and opinions, consumers don't know what to believe
Google "The Myths of Ethanol and Fuel Care" by Mercury Marine for this pdf.   Normal fuels cushion the valves Premium unleaded fuels provide a 'cushion' around each valve that stops the force of movement from damaging the valve.  This allows valves to keep their shape and run at maximum efficiency for longer. Ethanol-based fuels don't cushion the valves When valves aren't cushioned while the engine is running, they quickly get misshapen and will no longer seal correctly.  And we saw earlier that if the valves aren't working at peak efficiency, neither is the engine.  This is the primary reason that we recommend so strongly against the use of ethanol-based fuels – because the damage to a marine engine can be substantial even over a single tank of fuel at high RPM. Can't I just retune the engine? It's possible to retune a car engine to run on ethanol with minimal damage to its valves.  However, this doesn't translate too well to marine engines for a number of reasons:
  • Boat engines run at much higher RPMs – up to 3,000 rpm – than car engines.
  • Boat engines typically run under much higher loads than car engines.
  • Boat engines have only one gear.
These differences between car and marine engines mean that it isn't feasible to simply 'retune' a marine engine to cope with ethanol-based fuels. Condensation concerns Because a boat operates in the water, condensation is also an issue.  Ethanol absorbs moisture faster than other fuels – and this increases your chances of getting water in the engine.  We'll tell you more about how this affects the engine in a future blog post.  

Condensations Concerns: Facts

  • The truth is ethanol fuels help fuel systems stay dryer. How?  Straight gasoline E0 suspends .15 t-spoons (that's point-one-five) water before phase separation occurs.  Ethanol suspends 4 (that's four) t-spoons water before phase separation occurs or 26 times longer than E0. At 70°F and 70% relative humidity, about 2.7 months are required for straight gasoline to phase separate.  Do the math.  Ethanol - with 26 times more water-suspending capability – requires approximately 5.8 years storage with "open" fuel caps to phase separate.  Again, Mercury Marine states that "after the transition period from E0, E10 may actually be a superior marine fuel as it tends to keep low levels of water moving through the fuel system, keeping the system 'dry.'"
  • I see that SeaTechMarine is a Mercury Marine dealer and, as such, suggest they take a closer look at their OE supplier's statement re ethanol's assets before Blogging this subject.
  Summary Your marine engine isn't designed for ethanol-based fuels, and unlike a car engine, it can suffer severe damage quite quickly from them.  Avoid these fuels like the plague!  


Bobby Likis: I was surprised to read such a biased article from a company in the marine business.  Obviously, the author of this article is not informed in gasoline and/or ethanol-blended gasoline... certainly not remotely familiar with the facts re the history of leaded gasoline. Regardless, it's time the Marine Industry's own looked deeply into their opinions and beliefs and learned the facts.  I've operated an Automotive Service shop for 45 years and had more than 200,000 cars and small trucks pass thru my doors.  And not one ethanol-related engine loss have we seen...not one.  I can categorically state that ethanol blended gasoline is good for engines, enabling higher power and cleaner burning while reducing our country's dependence on foreign oil.  What's not to like!