Operating At High Elevations; Effects Of Elevation And Weather On Performance - Mercury 300XS OptiMax User Manual

If you keep your boat moored in the water, always tilt the outboard
so the gearcase is completely out of water (except in freezing
temperatures) when not in use.
Wash the outboard exterior and flush out the exhaust outlet of the
propeller and gearcase with fresh water after each use. Each
month, spray Mercury Precision or Quicksilver Corrosion Guard on
external metal surfaces. Do not spray on corrosion control anodes
as this will reduce the effectiveness of the anodes.

Operating at High Elevations

Your engine automatically compensates for high elevation
changes. A different pitch propeller may help reduce some normal
performance loss resulting from reduced oxygen in the air. Consult
your dealer.

Effects of Elevation and Weather on Performance

The following conditions lower engine performance and cannot be
compensated by the engine fuel or electronic management
systems.
• Above sea level elevations
• High temperature.
• Low barometric pressure.
• High humidity.
These conditions above reduce air density to the engine, which in
turn lowers the following:
• Boost pressure on supercharged engines
• Horsepower and torque throughout the RPM range
• Peak RPM
• Cranking compression
EXAMPLE: An engine run at an elevation of 8,000 feet will have
over a 30% power loss while a loss of engine power on a hot and
humid day could be as much as 14%.These losses apply to
normally aspirated and supercharged engines.
Compensating for power robbing conditions:
• Switch to lower pitch propeller.
• Change gear ratio.
OPERATION
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