I am assuming you have a carb 1993 mercury 200.
Page 191 shows jet chart. =>
http://www.hedges-uk.com/boat/Merc/o...0Magnum%20.pdf
3B-34 - FUEL SYSTEMS
90-824052R2 SEPTEMBER 1997
High Altitude Jet Chart
Factory installed main fuel jets are normally adequate for proper performance up to approximately 5000 feet
(1524m) above sea level. Between 2000 feet (609.6m) and 5000 feet (1524m) the reduction of the main fuel jet(s)
may result in improved performance and fuel economy. Above 5000 feet, however, it is recommended that main
jet size be reduced as shown per 1000 feet (304.8m) in the following chart.