Fuel Test Kit - Site Contents: E10 gas, disadvantages, benefits, precautions, history, renewable gasoline, marine, automobile...
Fuel Testers supplies the knowledge and resources you need to protect your engines from alcohol fuel - Auto, Marine, Aircraft....
Ethanol alcohol fuels in marine engines - Warnings and necessary precautions.
Ethanol alcohol, a renewable reformulated fuel, supports the farming industry and decreases U.S. dependence on foreign fuels.

Marine Outboard Driveability Effects of 10 and 20 % Ethanol on Engines: Marine Manufacturer Fuel Recommendations, 2003
Study by Orbital Engine Company February 2003. View online or Contact Fuel-Testers for a PDF copy.

Marine Manufacturer Fuel Recommendations: View Summary.
Herman & Associates, 2003. View online at ethanolrfa.org or Contact Fuel-Testers for a PDF copy.

LA Times - Class Action Lawsuit: "Boater sues over ethanol-laced gasoline's effect on fiberglass fuel tank"
View online at  www.kbklawyers.com/news/latimes_boater.pdf  or Contact Fuel-Testers for a PDF copy.
Ethanol alcohol blend fuels, made from corn & grains, can damage engines.
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E10 Problems in
Marine/Boat Engines

Portable, reusable Alcohol Fuel Test Kits protect marine engines by checking the ethanol/alcohol content of fuel, now used at most public gas pumps.

Be cautious when using E10 (ethanol/alcohol blend fuels) in marine and boat engines...

Ethanol alcohol  is a solvent, degreaser, cleanser, antifreeze and most problematic is ethanol's "hygroscopic" properties. Hygroscopic and miscible means ethanol attracts and absorbs water.

Ethanol fuels, (E10 and E85), rapidly absorb 50 times more water, than non-alcohol gas.

Alcohol fuels are not suitable for marine engine use...
Many have unsuccesfully requested government exemption for ethanol in marine engines. (aircraft fuels are exempt)
Unfortunately due to recent state and federal laws, you may have no other alternative than to purchase E10 (alcohol containing) gas at public gas stations.

Extra precautions are necessary when using fuels containing alcohol in boat engines.

Marine fuel system and gasoline rules have changed;
Since switching to alcohol oxygenated fuels.

Damage from ethanol's amazing water absorbing qualities is seen most often in the boating industry -

Boats love water but boat engines do not.  Boaters increase their risks even further, because they tend to store fuel in their boat gas tanks much longer than in their automobiles.  Fuel systems of cars also tend to have better seals, (EG. tightly closed gas caps).

Boat engines also are most used during the most humid (summer) months. Moisture from humid air can easily be absorbed into E10 fuel.

Alcohol/Ethanol being a solvent and de-greaser also adversely effects boat parts and components.
Clogging of carburetor and fuel filters is now more common.

Increased incidence of phase-separation due to water contamination now is a hige challenge for boaters.
Octane drops when fuel water contaminates, which makes fuel problems even more problematic.

Driveability and performance problems seem most noticeable in marine engines, motorcycles and older or classic cars.

Fuel Testers recommends testing gasoline (for ethanol and water) at the pump before purchase.
Alcohol Fuel Test Kits will assure gas contains 10% or less ethanol.

View List - E10 Engine Damage and Problems
Ethanol E10 Use in Marine Engines
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Alcohol in E10 ethanol gasoline has caused engine problems & damage, especially to marine, outboard and boat motors.

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Ethanol Alcohol Fuel Test Kits
Alcohol in E10 ethanol gasoline has caused engine problems & damage, especially to marine, outboard and boat motors...
Report E10 Gas/Engine Problems
Report gasoline that contains ethanol above the legal limit of 10%.
Outboard & Marine Engine Precautions

View Top 20 List - General E10 Precautions

Marine engines require special  precautions to prevent water contamination from alcohol fuels.  Active fuel management is now required to protect marine engines from adverse effects of alcohol and to prevent water from entering fuel system.


  1. The most effective precautions you can take with alcohol blend fuels (E10 and E85) is to make sure you only run your engine on clean, new, fresh fuel, if non-alcohol fuel is not available in your area. 
We recommend re-filling fuel tank every 1-3 weeks, when using ethanol blend fuels, to avoid excess water absorption.

In 100 days or less, under ideal conditions (low humidity, sealed fuel system) the alcohol composition of gasoline will absorb enough water to cause gas contamination.  In reality, marine engines will experience contaminated fuel much sooner.

When E10 fuel experiences water conatamination octane will decrease up to 3 points, sometimes referred to as "lean fuel". 

  1. Maintain a sealed fuel tank, and avoid gas tank  and fuel lines from unnecessarily coming in contact with water.
  2. Keep engine parts well lubricated to decrease the drying effects on engine parts, especially plastic and rubber parts.
  3. Frequently check gasoline for Water Contamination (WC) and Phase Separation (PS)-
  4. Properly discard any fuel that appears to have gone bad.  Resist the temptation to use bad gas in other gas-powered equipment.
  5. Keep your engine tuned and follow the manufacturers recommended maintenance schedule.
  6. For extra protection, buy gasoline with a higher octane to be certain that you will always be running your engine on the minimum octane necessary for good performance.

When PS and WC occurs, octane can drop as much as 3 points.  While some may disagree, unless you're 100% certain your fuel is good, I firmly believe a higher octane prevents the sudden onset of performance issues, in the event the gas suddenly enters a phase separated state when traveling in ocean/lakes/waterways.

       - Most newer engines (past 5-10 years) are designed to tolerate 10% or lower alcohol in gasoline.
       - Older engines usually do not have a factory installed water separating filter - Check your filters and install the best available, (10-12 mm).

Ethanol's Water Absorbing Qualities

10% ethanol gasoline is hygroscopic (will absorb water) and can absorb 50 times more water than conventional non-alcohol gasoline.
       - Phase separation occurs in E10 gas, when only 0.5% water or 3.8 teaspoons water per gallon of fuel is absorbed.

At 70 degrees Fahrenheit, E10 gasoline can dissolve up to 6000-7000 parts per million (ppm) water.
When this blend is cooled, both the water and some of the ethanol become insoluble.

Phase Separation

With the process of phase separation, two layers of liquid are visible.
- An upper ethanol-deficient gasoline layer and a lower ethanol-rich (up to 75% ethanol) water layer.

It occurs because ethanol is completely soluble in water but only marginally soluble in hydrocarbons...
After phase separation, the gasoline layer will have a lower octane number. The fuel also is less volatile.

Shelf Life

Ethanol fuel expires in 90-100 days, under ideal environmental conditions (low humidity). 

Removal of Water from Phase Separated  E10 Fuel

It is not safe to simply remove water from bottom of tank (after phase separation) when tank contains E10 fuel. Because ethanol joins with water (drops to bottom of tank), when you drain lower layer you are also removing octane enhancing ethanol. Octane will drop about 2-4 points in the upper petroleum layer. More water removal information...

When using E10 ethanol alcohol fuels, special precautions are necessary with marine engines because:

       - E10 and E85 ethanol blend fuels have an affinity to absorb amazing amounts of water, very quickly, compared to conventional non-alcohol gasoline.
       - Ethanol alcohol is a great solvent and cleaner, that can dissolve engine parts (rubber, plastic, aluminum, and certain fiberglass tanks), dry out hoses, remove lubrication, and more.
       - Engine seals and hoses shrink, swell, or lose strength when exposed to ethanol reformulated gasoline.
       - Water is actually dissolved in an ethanol blended fuel and phase separation occurs much sooner. With MTBE, ETBE, lead and other chemicals used in the past to oxygenated gasoline, this did not happen.
       - The shelf life of ethanol blend fuels is much lower due to it's water-absorbing and corrosive qualities.  Replacing gasoline every 2 to 4 weeks is usually recommended with E10.   90 days is the maximum shelf-life recommended. 
       - The amount of ethanol blended in at the pumps, is not closely monitored. Checking gasoline meets safe and legal alcohol guidelines (10% or lower), seems necessary now, until more stringent and protective laws are passed.

With the knowledge on how ethanol behaves and some necessary precautions and careful monitoring, you can limit the problems you may encounter when using E10 gasoline in most most marine engines.
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