GASOLINE ENGINE 8.1 S INBOARD MODELS
Page 10 of 58
COMBUSTION AIR REQUIREMENTS
Engine compartments with natural draft ventilation must have vent openings of sufficient
size and location to accomplish the tasks previously outlined.
IMPORTANT: The size of ventilation openings must be increased if any auxiliary
equipment is located in the engine compartment.
The combustion air requirement (per engine) for the specified engines at WOT are given
in the chart below:
Combustion Air Requirements (Per Engine)
Model
Engine Air Requirements at
WOT
Engine Physical Volume
8.1S HO
726 ft
3
/min. (0.342 m
3
/sec)
6.0 ft
3
(170 l)
8.1S Horizon
657 ft
3
/min.(.3 m
3
/sec.)
6.0 ft
3
(170 l)
The pressure differential between outside and inside the engine compartment must not
exceed the following value.
Maximum Pressure Differential at WOT
2 in. (51 mm) of water (measured with a manometer)
TEMPERATURE
Air temperatures inside the engine compartments have been measured in excess of
200
°
F (82
°
C). The long term effect to fuel system components running at these
excessive temperatures is not known.
According to specification SAE J1223 for Marine Carburetors:
“The carburetor shall be capable of operation throughout an ambient (air temperature)
range from +20
°
to +176
°
F (–7
°
to +80
°
C) without failure.”
Carburetors, throttle body injection (TBI) units and components for multi-port EFI systems
used by Mercury MerCruiser meet this specification.
Under the hottest outside air temperature condition at which the boat will be operated, the
air temperature inside the engine compartment, measured at the flame arrestor, should not
exceed 176
°
F (80
°
C). Also, the temperature of the fuel being supplied to the engine should
not exceed 110
°
F (43
°
C) at any location between the fuel tank and the engine’s fuel pump.
Since many factors influence engine compartment temperature, temperature measure-
ments should always be carried out. Test as follows:
