Fuel system
2-46
Vapor separator
This model is equipped with a newly designed vapor separator, which has been changed to a sealed
type that eliminates the structure for discharging the vapor gas. Because venturi tubes “a” were added
to control the amount of vapor gas so that it does not exceed a certain level, the vapor gas can be
handled inside the vapor separator. When the liquid fuel is drawn from below the high-pressure fuel
pumps, the pressure of the fuel decreases when it passes through the venturi tubes because its flow
rate increases. As a result, it draws in the vapor gas from the passage at the top of each venturi tube.
Although this mixture of liquid fuel and vapor gas is drawn into the high-pressure fuel pumps in this
state, the vapor gas is compressed by the high-pressure fuel pumps into a liquid state and is dis-
charged as a liquid.
In addition, because the fuel pressure after the vapor separator is stabilized using feedback control,
the fuel return passage was eliminated.
As a result, the canister, return hoses, and other parts were eliminated, which reduced the number of
parts and improved serviceability.
Also, because the vapor gas is not released into the atmosphere, the outboard motor is friendlier on
the environment.
A. Liquid fuel flow
B. Vapor gas flow
C. Mixture of liquid fuel and vapor gas
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