5 - C
ONDITIONS
A
FFECTING
O
PERATION
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2
3
4
5
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Select a propeller that allows the engine to operate in the upper half
of the recommended full throttle RPM range with the boat normally
loaded (refer to
Specifications
).
If full throttle operation is below the recommended range, change
the propeller to prevent loss of performance and possible engine
damage. On the other hand, operating an engine above the
recommended operating RPM range causes higher than normal
wear or damage. "Propeller lines normally are designed so that the
next size pitch will change engine RPM by 300 to 500. For every 1"
of pitch change, the effect will be approximately 200 RPM."
RPM loss may require changing to a lower pitch propeller due
to the following conditions:
•
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.).
C
ONDITIONS
T
HAT
L
OWER
E
NGINE
P
ERFORMANCE
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.
Summary of Contents for Racing 1100 STERNDRIVE
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Page 27: ...2 GENERAL INFORMATION NOTES 20 90 8M0098854 MARCH 2015...
Page 43: ...5 CONDITIONS AFFECTING OPERATION NOTES 36 90 8M0098854 MARCH 2015...
Page 63: ...6 MAINTENANCE NOTES 56 90 8M0098854 MARCH 2015...
Page 71: ...8 OWNER SERVICE ASSISTANCE NOTES 64 90 8M0098854 MARCH 2015...
