Mercury 225 EFI, Service Manual

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EMISSIONS
Page 3D-4 90-884294 OCTOBER 2001
Stratified Charge
A stratified charge engine only pulls air through the transfer system. The fuel required for
combustion is forced into the cylinder through an injector placed in the top of the cylinder
(head). The injector sprays a fuel/air mixture in the form of a fuel cloud into the cylinder.
Surrounding this cloud is air supplied by the transfer system. As the cloud is ignited and
burns, the surrounding air provides almost complete combustion before the exhaust port
opens.
A stratified charge engine concentrates a rich mixture in the vicinity of the spark plug (air/
fuel ratio is less than 14.7:1). Elsewhere, the mixture is very lean or is comprised of air
only.
Emissions Information
Manufacturer’s Responsibility:
Beginning with 1998 model year engines, manufacturers of all marine propulsion engines
must determine the exhaust emission levels for each engine horsepower family and certi-
fy these engines with the United States Environmental Protection Agency (EPA). A certifi-
cation decal/emissions control information label, showing emission levels and engine
specifications directly related to emissions, must be placed on each engine at the time
of manufacture.