Cruising Rpm; Fuel Requirements; Fuel Ratings; Using Reformulated (Oxygenated) Gasolines (Usa Only) - Mercury Inboard 5.7L Manual

Specifications

Cruising RPM

Modern inboard engines operate at higher engine speeds than those produced just a few
years ago. This increased RPM along with better breathing is largely responsible for the
significant increase in horsepower of these new engines. Along with the higher WOT RPM
comes higher cruising RPM. This higher RPM is critical for optimum performance and
efficiency. The materials and design of the new engines allow these higher speeds without
durability penalty. In fact, over‑propping the boat to reduce the cruising RPM to previous
levels will increase the susceptibility to engine damage from detonation and pre‑ignition.
The recommended cruising RPM ranges are:
5.7L

Fuel Requirements

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
damage caused thereby will not be covered under the limited warranty.

Fuel Ratings

Mercury MerCruiser engines will operate satisfactorily when using a major brand of
unleaded gasoline meeting the following specifications:
USA and Canada ‑ having 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 ‑ having 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) Gasolines (USA Only)

This type of gasoline is required in certain areas of the USA. The 2 types of oxygenates
used in these fuels is Alcohol (Ethanol) or Ether (MTBE or ETBE). If Ethanol is the
oxygenate that is used in the gasoline in your area, refer to Gasolines Containing Alcohol.
These Reformulated Gasolines are acceptable for use in your Mercury MerCruiser engine.

Gasolines Containing Alcohol

If the gasoline in your area contains either methanol (methyl alcohol) or ethanol (ethyl
alcohol), you should be aware of certain adverse effects that can occur. These adverse
effects are more severe with methanol. Increasing the percentage of alcohol in the fuel can
also worsen these adverse effects.
Some of these adverse effects are caused because the alcohol in the gasoline can absorb
moisture from the air, resulting in a separation of the water/alcohol from the gasoline in the
fuel tank.
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 the boat's
fuel system components (fuel tanks, fuel lines, and fittings). Be aware that gasolines
containing alcohol may cause increased:
• Corrosion of metal parts
• Deterioration of rubber or plastic parts
Page 34
Cruising RPM for Peak Efficiency
Model RPM Range
3200‑3600
90-860174050 JUNE 2005