Propeller Selection - FNM HPEP 225 Installation Manual

Propeller Selection

IMPORTANT: Installed propeller must allow engine to run at the upper end of the
specified wide open throttle operating revolutions per minute (rpm) range, with a
normal load aboard the boat. Use an accurate service tachometer to verify engine
operating rpm.
It is the responsibility of the boat manufacturer and/or the selling dealer to equip the power
package with the correct propellers.
Select a propeller that will allow the engine power package to operate at or near the top end
of the specified WOT operating rpm range with a normal load. High rpm, caused by an
excessive trim angle, should not be used in determining correct propeller selection.
If full throttle operation is below the specified range, the propeller must be changed to
prevent loss of performance and possible engine damage. On the other hand, operating an
engine above the specified operating rpm range will cause higher than normal wear and/or
damage.
After initial propeller selection, the following common problems may require that the
propeller be changed to a lower pitch:
•
•
•
For better acceleration, such as is needed for water skiing, use the next lower pitch
propeller. Do not operate at full throttle when using the lower pitch propeller but not pulling
skiers.
Because of the many variables of boat design, only testing will determine the best propeller
for a particular application.
See BOAT IN THE WATER TESTS, Maximum RPM Test in the power package
Installation Manual.
Warmer weather and greater humidity cause an rpm loss (not as significant on EDI
models).
Operating in a higher elevation causes an rpm loss.
Operating with increased load (additional passengers, pulling skiers).
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