Hamilton Jet HJ241, Manual

Page: 28 / 202

2.6
2 SYSTEM OPERATION
2.5 C
RUISING
HJ-241 / HSRX
2.5 CRUISING
Care must be taken to prevent cavitation damage
to the Jet Units, as described below:
1. Running at speed with a partially blocked Inlet
Grill or debris on the Impeller will result in
cavitation damage to the Jet Unit. Before
accelerating to full speed, all Jet Units should be
cleared of debris.
Refer to Section 2.9 Blockages
(Debris in the Jet Unit) .
2. Acceleration should be carried out gradually.
Full power cannot be used at low vessel speeds
such as when operating on one engine only.
3. If there is any blockage of the Jet Unit, the engine
will run at a higher than normal RPM and the
vessel will accelerate slowly, and best speed will
be reduced. If such symptoms are noticed,
immediately slow the vessel and clear the
blockage.
Section 2.9 Blockages (Debris in the Jet
Unit) refers.
4. In conditions of severe weather or overload, the
engine speed should be reduced accordingly.
2.6 SHALLOW WATER
OPERATION
It is important to avoid pumping stones, sand etc.
through the Jet Unit as this will blunt and wear the
Impeller. The following diagrams illustrate good
and bad practice:
1. At high planing speeds, shallow water operation
is not a problem until the vessel is nearly
grounded.
2. At slow displacement speed avoid using high
RPM in shallow water.
3. If it is not possible to pick a deep-water area to
start off and stop in then "idle" over the shallow
area into deep water before accelerating up to
planing speed. If any debris has been picked up
in the intake screen, momentarily stopping the
engine should allow the debris to drop away from
screen.
C
AUTION
Running at speed with a partially
blocked inlet grill or debris on the
impeller will result in cavitation
damage to the jet unit.
C
AUTION
Do not run the Jet Unit if the
vessel has run aground as damage
may occur to the Impellers and
Stator.
Figure 6: High Speed Planing in Shallow Water
Figure 7: Shallow Water Operation Slow Speed
Figure 8: Shallow Water Operation Idle
RPM
KNOTS
RPM
KNOTS
RPM
KNOTS