Propeller Selection; Procedure - BRP Johnson J30TEL4SUA 2007 Service Manual

INSTALLATION AND PREDELIVERY

PROPELLER SELECTION

PROPELLER SELECTION
Refer to Propeller Hardware Installation on
p. 49 before installing propeller.
The correct propeller, under normal load condi-
tions, will allow the engine to run near the mid-
point of the RPM operating range at full throttle.
Refer to TECHNICAL DATA on p. 16.
1
6
2
1. Percentage of horsepower (kw)
2. Engine RPM
3. Horsepower curve
4. Full throttle operating range
5. Midpoint of full throttle operating range, horse-
power rating in kilowatts (kw))
6. Engine is overloaded at full throttle
7. Engine is overspeeding at full throttle
CAUTION
Selection of the wrong propeller could
reduce engine service life, affect boat per-
formance, or cause serious damage to the
powerhead.
48
5
3
7
4
DR1261

Procedure

The propeller selection process is very important
to the engine's service life and to boat perfor-
mance. Proceed carefully and thoroughly while
considering the following points:
•
During the engine break-in period, run the out-
board at wide-open throttle for only brief periods
of time to check full-throttle RPM.
•
Use an accurate tachometer to determine the
engine's full-throttle RPM while testing various
propellers.
•
Select a propeller that suits the customer's
application and allows the engine to run near
the midpoint of the full-throttle operating range
when the boat has a normal load in it. Refer to
TECHNICAL DATA on p. 16.
•
To compensate for changes in boat loading, the
engine's full-throttle RPM must be verified peri-
odically.
IMPORTANT:
If the propeller blades have too
much pitch, the engine is operating below its nor-
mal range at full throttle, power is being lost, and
powerhead damage could occur. If the propeller
blades have too little pitch, the engine is operating
above its normal range at full throttle and damage
from overspeeding could occur.
WARNING
When servicing the propeller, always shift
the outboard to NEUTRAL, turn the key
switch OFF, and twist and remove all spark
plug leads so the engine cannot be started
accidentally.