Propeller; Propeller Selection - Honda BF75D Manual

13. PROPELLER

Propeller Selection

PITCH
Recommended full throttle engine speed range:
BF75D: 5,000 – 6,000 min
BF90D: 5,300 – 6,300 min
Engine speed varies with propeller size and boat
condition.
A propeller must be selected to adjust maximum
engine speed to the recommended engine speed
range.
Using the wrong propeller can cause motor damage.
The proper propeller will assure powerful acceleration,
top speed, good fuel economy, cruising comfort, and
engine service life.
Propeller Selection Precaution
• Outboard motor must be installed vertically in
relation to boat bottom. Set moderate trim angle,
and adjust power trim angle to lowest setting.
• Set trim tab, so boat will run in a straight line.
• Protect propeller from foreign objects, check
regularly for damage, and/or deformation, and
aquatic plants wrapped around propeller hub.
• Keep bottom clean of shells, algae froth and dirt.
These will cause a significant drop in top speed.
• When doing propeller checks, select a calm day with
little waves action.
• Avoid strong winds. Wind speed should be less than
15 km/h (10 miles/h).
• The boat should carry its average load (crew, load
arrangement, ballast).
Pitch ..................Advanced Distance During One Turn (Apparent
Pitch Ratio......... P
Slip Ratio .......... (Visual Advanced Distance – Measured Distance) x 100
During running; the actually advanced distance is reduced by about 10
– 15% due to propeller display pitch.
PROPELLER DIMENSIONS
(Diameter x Pitch)
–1
–1
Advanced Distance)
P: Pitch (mm)
D D: Outer Diameter of Propeller
Visual Advanced Distance
Select the correct propeller so that full throttle engine
speed is within the recommended range.
• If the engine min –1 is under the recommended min
range, lower the propeller pitch by one size (1 to 2
inches) or more as needed.
• If the engine min
–1
range, select a propeller with a pitch one size larger
or as needed.
• If the following conditions exist, acceleration will
improve and outboard motor service life will increase
by lowering the propeller pitch.
– Heavy loads such as crew, load, equipment, water
skiing, etc;
– High temperatures and high humidity conditions;
– When operating at high altitude;
– When boat bottom needs cleaning;
– When area around gear case is obstructed;
To increase motor service life and ensure safe
navigation, do not use full throttle for extended
periods, but run the motor at 70 to 80% of full throttle.
NOTICE
If full throttle engine min
range, it can cause increased vibration, noise,
reduced boat performance, and possible engine wear
damage.
If full throttle engine min
range, it indicates that the engine is being overloaded.
44
is over the recommended min
-1 exceeds the recommended
is below the recommended
–1
–1
–1