1997+ Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-826148R2, Page 154Get this manual
Rejetting Carburetors For High Altitude Operation The carburetor jet installed at the manufacturer is for engine operation at sea level through an elevation of 2500 feet (762m) above sea levelIf the engine is to be operated at an altitude higher than 2500 feet above sea level, it will be necessary to rejet (remove the carburetor jets and install jets with different orifice size) the carburetorsEach time the engine is to be operated at different elevation from the previous time, refer to the "Carburetor Jet Charts" following, and rejet the carburetors for elevation engine will be operated atHigh Altitude Jet Chart Engine Operation Elevation (Above Sea Level) 2500'5000' (7501500m) 5000'7500' (15002250m) 7500' and Up (2250m and Up) High Speed Jet Size .002" smaller (than standard jet) .004" smaller (than standard jet) .006" smaller (than standard jet)