High Altitude Operation - Honda BF25A Owner's Manual

7. OPERATION
High Altitude Operation
At high altitude, the standard carburetor air-fuel mixture
will be too rich. Performance will decrease, and fuel con-
sumption will increase. A very rich mixture will also foul
the spark plug and cause hard starting.
High altitude performance can be improved by specific modifi-
cations to the carburetors. If you always operate your outboard
at altitudes above 5,000 feet (1,524 meters) have an authorized
Honda Marine or Outboard Motor dealer perform this
carburetor modification.
Even with carburetor modification, engine horsepower
will decrease about 3.5% for each 1,000 foot (300 meter)
increase in altitude. The effect of altitude on horsepower
will be greater than this if no carburetor modification is
made.
1-1 When the carburetors have 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
(I 524 meters) with modified carburetors may cause the engine
to overheat and result in serious engine damage. For use at
low altitudes, have an authorized Honda Marine or Outboard
Motor dealer return the carburetors to original factory specif-
cations.
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