Specifications; Fuel Recommendations - Mercury MerCruiser MCM 4.3L ALPHA Service Manual

MAINTENANCE
CA261

Specifications

Fuel Recommendations

IMPORTANT: Use of improper gasoline can damage your engine seriously. Engine
damage resulting from use of improper gasoline is considered misuse of 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 as follows:
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.
CA291
USING REFORMULATED (OXYGENATED) GASOLINES (USA ONLY)
This type of gasoline is required in certain areas of the USA. The two types of "oxygenates"
used in these fuels are Alcohol (Ethanol) or Ether (MTBE or ETBE). If Ethanol is the "oxygen-
ate" 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.
VAPOR LOCKING
Fuels containing alcohol and winter grade fuels will aggravate vapor lock problems. A vapor
lock condition can be identified by the following problems:
• Engine starts and, upon advancing throttle, shuts off and will not restart.
• If engine does restart, it shuts off when advancing throttle.
• Engine is difficult to restart after operating the boat and then leaving the engine off for 1 to
3 hours.
Other factors may combine to increase vapor locking. These factors include but are not lim-
ited to:
• air temperature
• fuel tank location
• fuel supply system
• engine coolant temperature
• temperature and vacuum of fuel to engine
• engine compartment air temperature and ventilation
Other conditions should be ruled out before treating the problem as vapor locking.
Index
Page 1B-8
SERVICE MANUAL NUMBER 25
90-861328--1 NOVEMBER 1999