Mercury Racing HP525 EFI Bravo Sterndrive Series, Operation, Maintenance & Warranty Manual

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CONDITIONS AFFECTING OPERATION
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• Operating in warmer weather and greater humidity.
• Operating in a higher elevation.
• Operating with a damaged propeller or dirty boat bottom.
• Operating with increased load (additional passengers,
pulling skiers, etc.).
Conditions That Lower Engine 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.
The conditions listed above reduce air density to the engine
which in turn reduces the following:
• Boost pressure on supercharged engines
• Horsepower and torque throughout the RPM range
• Peak RPM
• Cranking compression
EXAMPLE: An engine running at an elevation of 2,438 m (8,000
ft) will have over a 30% power loss while engine power on a hot
and humid day can be reduced by as much as 14%. These
losses apply to both normally aspirated and supercharged
engines.
Compensating for power robbing conditions:
• Switch to a lower pitch propeller.
• Change the gear ratio.
Some boat performance can be regained by dropping to a lower
pitch propeller, but engine performance will remain lower. In
some cases, a gear ratio reduction may be more beneficial. To
optimize engine performance, prop the engine to allow operation
at or near the top end of the recommended maximum RPM
range at wide open throttle with a normal boat load.