Hamilton Jet HJ241, Manual

Page: 68 / 202

5.8
5 INSTALLATION
5.6 D
RIVELINE AND
E
NGINE
I
NSTALLATION
HJ-241 / HSRX
5.6.2 Engine Cooling
The engine may be cooled conventionally or by
making use of the BSP inboard water offtake from
the Jet. The Jet is supplied with the water offtake
plugged by a combined Plug / Hosetail. To convert
the Plug to a Hosetail, the end of the Plug is cut off
with a hacksaw and the cooling system plumbed
from the Hosetail.
Refer to Section 3.7.3 Cooling .
There is a 1¼" BSP outboard water offtake which
provides water at approximately 10 kPa (1½ psi) at
600 RPM and up to 31kPa (45 psi) at - 260 Kw (350
hp) -
refer to Section 3.5 Water Off-Take . The water
may be fed directly to the engine without the need
for a raw water pump, provided that:
4. The pressure from the water offtake at idle is
sufficient to cool the engine.
5. The engine can withstand the full pressure from
the water offtake.
• To be sure of correct flow for engine cool-
ing, a conventional water pick up and the
engine raw water pump should be used.
• The Jet Unit water offtake can be used for
a deck cleaning hose but the pressure is
not high enough for a fire hose. The jet is
supplied with the water offtake plugged.
If shallow water operation is anticipated a sand trap
should be installed in the cooling line to prevent
sand from clogging the cooling system. A Sand Trap
Kit can be purchased from C.W.F. Hamilton & Co.
Ltd.
(Drawing HJ-241-12-000 Sandtrap & engine
Cooling refers).
It is common to use a heat exchanger and a separate
cooling water circuit for the engine so that the river
or seawater does not enter the engine. In this case
the cooling water from the jet water offtake goes
through the heat exchanger circuit.
5.6.3 Engine Systems
Refer to Section 3.7.4 Engine Systems .
5.6.4 Exhaust Systems
Refer to Section 3.7.4 Engine Systems .
5.6.5 Governor Settings
The "No Load" governor setting (or "High Idle") on
diesel engines, should be set well clear of the full
throttle R.P.M. achieved when driving the Jet Unit so
that there is no chance of the governor reducing
power (and performance) at full throttle. To check,
select neutral if clutch or gearbox fitted but without
these unbolt the driveline at the engine flywheel and
open the throttle fully. To accurately measure RPM,
use a calibrated hand tachometer.
EXAMPLE:
If the maximum RPM for driving the Jet Unit
is 2800 RPM, then the governor should not
begin to operate until at least 2850 RPM.
On most diesel engines this means the "No
Load Governor Setting" (or "High Idle")
should be at least 3050 RPM. (i.e. 250 RPM
higher than the loaded maximum RPM).
Ensure that the low idle RPM is set high enough to
avoid any vibration in the driveline. Extensive idling
with the driveline vibrating may damage the Jet Unit.
Refer to Section 3.3 Drivelines .
C
AUTION
If a gearbox or clutch is fitted to
the engine, a conventional hull
water pick-up and engine raw
water pump must be used.
C
AUTION
Ensure that the engine cooling
water pick up is not directly
ahead of the Jet Unit Intake, but
well to the side to avoid turbulent
water flow into the Jet.