High Altitude Operation - Honda Outboard Motors 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.
NOTICE
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
(1,524 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 specifications.