Section 4 - Specifications
Page 54 90-899883173 DECEMBER 2007
Cruising RPM
Material and design advancements allow modern inboard engines operate at higher engine
speeds than their predecessors. Increased RPM significantly increases the horsepower of
these new engines and is a critical part performance and efficiency. The materials and
design of the new engines allow these higher speeds without durability penalty.
Over‑propping the boat to reduce its cruising RPM to previous levels increases the engine's
susceptibility to engine damage from detonation and pre‑ignition. The recommended
cruising RPM ranges are:
Cruising RPM for peak efficiency
Model RPM range
5.7 MPI and Horizon 5.7 3400–3800
Fuel Requirements
NOTICE
Running out of fuel can damage catalyst components. Do not allow the fuel tanks to
become empty during operation.
IMPORTANT: Use of improper gasoline can damage your engine. Engine damage
resulting from the use of improper gasoline is considered misuse of the engine and
will not be covered under the limited warranty.
Fuel Ratings
Mercury MerCruiser engines will operate satisfactorily with any major brand of unleaded
gasoline that meets the following specifications:
USA and Canada ‑ A posted pump Octane Rating of 87 (R+M)/2, minimum. Premium
gasoline [92 (R+M)/2 Octane] is also acceptable. Do not use leaded gasoline.
Outside USA and Canada ‑ A posted pump Octane Rating of 90 RON, minimum. Premium
gasoline (98 RON) is also acceptable. If unleaded gasoline is not available, use a major
brand of leaded gasoline.
Using Reformulated (Oxygenated) Gasoline (USA Only)
Reformulated gasoline is required in certain areas of the USA and are 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 Alcohol.
Gasoline Containing Alcohol
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:
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