Carburetor Modification For High Altitude Operation - Honda BF5A Owner's Manual

TECHNICAL & CONSUMER INFORMATION
Carburetor Modification for High Altitude Operation
At high altitude, the standard carburetor air-fuel mixture will be too rich.
Performance will decrease, and fuel consumption will increase. A very rich
mixture will also foul the spark plug and cause hard starting.
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High altitude performance can be improved by specific modifications to the
carburetor. If you always operate your engine at altitudes above 5,000 feet
(1,500 meters), have an authorized Honda marine dealer perform this carbu-
retor modification.
Even with carburetor modification, engine horsepower will decrease about
3.5%for each 1 ,OOO-foot (300-meter) increase in altitude. The effect of altitude
on horsepower will be greater than this if no carburetor modification is made.
When the carburetor has been modified for high altitude operation, the air-fuel
mixture will be too lean for low altitude use. Operation at altitudes below 5,000
feet (1,500 meters) with a modified carburetor may cause the engine to
overheat and result in serious engine damage. For use at low altitudes, have
an authorized Honda marine dealer return the carburetor to original factory
specifications.
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