Mercury 5.7 TowSport MPI, Manual

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Section 4 - Specifications
Page 36 90-8M0086943
eng
DECEMBER 2014
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 preignition.
The recommended cruising RPM ranges are:
Cruising RPM for Peak Efficiency
Model RPM Range
5.7 LHS 3200–3600
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.
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
• Fuel permeation through 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.
Because of possible adverse effects of alcohol in gasoline, it is recommended that only alcohol‑free gasoline be used where
possible. If only fuel containing alcohol is available, or if the presence of alcohol is unknown, increased inspection frequency for
leaks and abnormalities is required.
IMPORTANT: When operating a Mercury MerCruiser engine on gasoline containing alcohol, storage of gasoline in the fuel tank
for long periods should be avoided. Long periods of storage, common to boats, create unique problems. In cars alcohol‑blend
fuels normally are consumed before they can absorb enough moisture to cause trouble, but boats often sit idle long enough for
phase separation to take place. In addition, internal corrosion may take place during storage if alcohol has washed protective
oil films from internal components.
Engine Oil
For optimum engine performance and maximum protection, use the following oil: