Using an Ethanol Fuel Tester is crucial for maintaining the fuel quality in legacy two-stroke outboards from Mercury, Yamaha, OMC, Johnson, Evinrude, and Tohatsu is a best practice.
Ethanol causes fuel separation, varnish (sticky tar) buildup, and damage to carburetors, fuel lines, and seals, making it essential to check ethanol content before use.
Step-by-Step Guide to Testing Ethanol in Your Fuel
What You’ll Need:
✔ Ethanol Fuel Tester (a clear graduated test tube with ethanol percentage markings)
✔ Gasoline sample (from your fuel tank, gas can, or station pump)
✔ Water (preferably distilled for accuracy)
Instructions:
1. Fill the Tester with Water
Locate the water fill line near the bottom of the tester.
Pour clean water up to the indicated line.
2. Add Your Gasoline Sample
Slowly pour your fuel sample into the tester until it reaches the gasoline fill line (usually near the top).
Avoid overfilling or spilling.
3. Seal and Shake the Tester
Secure the cap tightly.
Shake the tester gently for 30-60 seconds to mix the gasoline and water.
Set the tester on a flat surface and allow the fuel to separate.
4. Let the Fuel Settle
Wait about 5-10 minutes for separation to occur.
The water will pull the ethanol from the gasoline, settling at the bottom.
The pure gasoline will remain on top.
5. Read the Ethanol Content
Check the new water level after settling.
The increase in water volume represents the percentage of ethanol in your fuel.
Example: If the water level rises to the 10% mark, your fuel contains 10% ethanol (E10).
Interpreting Your Test Results for Legacy 2-Stroke Outboards
✅ 0% (E0) – Ethanol-free fuel (best for legacy two-stroke engines, prevents carburetor issues).
✅ Up to 10% (E10) – Most outboards can tolerate this but require fresh and proper fuel blends or additives.
⚠ Above 10% (E15, E20, E85, etc.) – Not recommended for older two-stroke outboards, as it can cause fuel phase separation, lean running conditions, and engine damage.
Why Legacy 2-Stroke Outboards Need Ethanol Testing
Prevents fuel breakdown that leads to carburetor blockages.
Reduces risk of fuel line degradation caused by ethanol.
Ensures proper fuel/oil mixture stability for smooth performance.
Avoids phase separation, which can cause hard starts, poor idling, and engine stalling.
Protects seals and gaskets in vintage Mercury, Yamaha, OMC, Johnson, Evinrude, and Tohatsu two-stroke engines.
Recommended Fuel Options for Legacy 2-Stroke Outboards
To maintain optimal performance and longevity, using recreational (REC) non-ethanol pump gas (typically 89 or 90 Octane), race fuels, or a blend of these fuels is highly recommended.
Non-ethanol fuel eliminates the risks of phase separation, corrosion, and degradation commonly associated with ethanol-blended fuels. Race fuels provide higher octane stability, which can benefit high-performance applications.
A custom blend of non-ethanol pump gas and race fuel can offer a balance of affordability, protection, and performance, ensuring smooth operation for legacy two-stroke marine engines.
By regularly testing ethanol content and selecting the right fuel, you can extend the life of your outboard engine, maintain peak performance, and reduce costly carb rebuilds, fuel injector cleaning service fuel system and fuel line replacements and repairs. 🚤⚙️🔧
Don't leave the dock with-out it.!😎