Mercury 90 - Outboard Hydrocarbon Emissions Reductions

3D-2 - FUEL SYSTEM 90-830234R3 DECEMBER 1997
As the air/fuel ratio becomes leaner, combustion
temperatures increase. Higher combustion temper-
atures raise the NOx content of the exhaust. But,
enrichening the air/fuel ratio to decrease combus-
tion temperatures and reduce NOx also increases
HC and CO, as well as lowering fuel economy. So the
solution to controlling NOx - as well as HC and CO -
is to keep the air/fuel ratio as close to 14.7:1 as pos-
sible.
OUTBOARD HYDROCARBON
EMISSIONS REDUCTIONS
8 1/3%  PER YEAR OVER 9 MODEL YEARS
0
20
40
60
80
100
120
96 97 98 99 2000 01 02 03 04 05 06 07 08