Page 13 - REPOWER REFERENCE GUIDE (2020)

Important Information

Using I-16 Biobutanol Fuel Blends (USA Only)
I‑16 Biobutanol fuel blends of up to 16.1 vol percent that meet the published Mercury MerCruiser Fuel Rating requirements are
an acceptable substitute for unleaded gasoline. Contact your boat manufacturer for specific recommendations on your boat's
fuel system components (fuel tanks, fuel lines, and fittings).
Using Reformulated (Oxygenated) Gasoline (USA Only)
Reformulated gasoline is required in certain areas of the USA and is acceptable for use in your Mercury MerCruiser engine.
The two types of oxygenates used in these fuels are alcohol (ethanol) and ether (MTBE or ETBE). If ethanol is the oxygenate
that is used in the gasoline in your area, refer to Gasoline Containing Methanol or Ethanol.
Gasoline Containing Methanol or Ethanol
If the gasoline in your area contains either methanol (methyl alcohol) or ethanol (ethyl alcohol), be aware of possible adverse
effects. These adverse effects are more severe with methanol and worsen according to the percentage of alcohol in the fuel.
Alcohol in gasoline can absorb moisture from the air, causing the water and the alcohol to separate from the gasoline in the fuel
tank.
IMPORTANT: The fuel system components on your Mercury MerCruiser engine will withstand up to 10% alcohol content in the
gasoline. We do not know what percentage your boat's fuel system will withstand. Contact your boat manufacturer for specific
recommendations on your boat's fuel system components (fuel tanks, fuel lines, and fittings).
Be aware that gasoline containing alcohol may cause increased:
• Corrosion of metal parts
• Deterioration of rubber or plastic parts
• Fuel permeation through the rubber fuel lines
• Starting and operating difficulties
! WARNING

Fuel leakage is a fire or explosion hazard, which can cause serious injury or death. Periodically inspect all fuel system
components for leaks, softening, hardening, swelling, or corrosion, particularly after storage. Any sign of leakage or
deterioration requires replacement before further engine operation.

IMPORTANT: If you use gasoline that contains or might contain alcohol, you must increase the frequency of inspection for
leaks and abnormalities.
IMPORTANT: When operating a Mercury MerCruiser engine on gasoline containing alcohol, do not store the gasoline in the
fuel tank for long periods. Cars normally consume alcohol‑blend fuels before they can absorb enough moisture to cause
trouble, boats often sit idle long enough for phase separation to take place. Internal corrosion may take place during storage if
alcohol has washed protective oil films from internal components.

Testing For Alcohol in Fuel
An ethanol test kit (91-879172T28) is available from Mercury Marine. Alternately, a syringe graduated in cubic centimeters (cc)
that will hold 12 cc or more can be used; obtain locally.
Procedure for Using a Syringe
1. Draw approximately 6 cc of water into the syringe. Point the syringe upward and squirt out all but 3 cc. Squirting out the
extra water removes the unwanted air from the syringe.
2. Draw the fuel to be tested into the syringe up to the 12 cc mark.
3. Close off the tip of the syringe with your finger and shake the syringe to mix the fuel and water. Slowly remove your finger
to relieve the pressure.
4. Stand the syringe on a flat surface for about a minute. Be sure to keep the tip up.
5. After a minute has passed, examine the syringe. If alcohol is in the fuel, it will have bonded with the water and settled to
the bottom of the syringe.
6. Use the chart below to determine the percentage of alcohol in the gasoline.

Volume of gasoline Percentage of alcohol
9.0 cc 0%
8.6 cc 5%
8.1 cc 10%
7.7 cc 15%
7.2 cc 20%

90-8M0149179 eng NOVEMBER 2018 © 2019 Mercury Marine Page 1B-3