4 cylinders + 6 cylinders 4 cylinders + 6 cylinders - Steyr Motors

ToC
05 COOLING SYSTEM
SERVICE MANUAL MARINE ENGINES
05.00. FUNCTIONAL DESCRIPTION COOLING CIRCUIT
05.00.01 Raw water circuit (external cooling circuit)
Raw water is fed to the engine via a vane-type pump in the secondary circuit. The raw water pump
(ill.1/2) is a self-sucking pump and is driven for 4 cyl. engines via Poly-V-belts and for 6 cyl. engines
via V-belt. The impeller is arranged eccentrically.
At higher speeds, it acts as combinded centrifugal- and displacement pump. At slow speeds, the
impeller acts as displacement pump. This causes a pump effect of the impeller wings during operation
of the engine. At high engine speed, the resistance of water on its way through the pump is sufficient
to avoid a contact of the impeller wing with the inner side of housing. The wings are only bent inside
in direction of impeller center, thus acting as combined centrifugal- and displacement pump.
Raw water is fed to the raw water pump via raw water pick-up (ill.1/1) and/or via drive unit (Z-drive, jetdrive)
and/or raw water filter (ill.1/11) arranged between. From the raw water pump, water flows into
the combined fuel- (ill.1/3) and steering- and/or transmission oil cooler (ill.1/4) where the raw water
absorbs thermal energy from the fuel- and steering- and/or transmission oil system.
Then water flows through the tube stake of intercooler (ill. 1/5) where the raw water absorbs thermal
energy from air charge.
Through the connecting line above the rear part of the camshaft case the raw water enters the tube
stake of heat exchanger (ill.1/6) where the raw water still absorbs thermical energy from engine
coolant.
Then raw water flows through the high-riser (ill.1/7) where the raw water still absorbs thermal energy
from exhaust gas, and finally leaves, mixed with exhaust gas, the raw water circuit via exhaust pipe
(raw water outlet) (ill. 1/9) either through the drive or a muffler, and is blown in below water surface.
The splash water flap (ill.1/12) avoids a possible raw water entry with stopped engine.
The raw water circuit is equipped with 5 sacrificial anodes (ill.1/10) (for salt water made of zinc; for sea
water magnesium anodes are recommended).
Temperature of raw water, mixed with exhaust gas, is controlled by means of sensor (ill.1/8) on highriser
and transmitted to the electronic management system. If during operation the limit of 60°C is
exceeded, the electronic management system will reduce the engine power to a perceptible extent of
up to 50%.
This disturbance will be indicated on the instrument panel by means of signal lamp for engine check
which blinks 2 times/sec. and an audible warner (2times/sec).
ATTENTION:
To exclude consecutive damages, occured trouble should be analyzed and eliminated
as soon as possible.
Page COOLING SYSTEM - 2 Z001019/0_6_July 2008