18889 1 Mercury GASKET, SOUND ATTENUATOR

Unburned gas in the air inlet and exhaust system may ignite when the engine is started. Personal injury and/or property damage may result.Before starting an engine that may contain unburned gas, purge the unburned gas from the air inlet and exhaust system. Refer to the topic on purging unburned gas in the "Starting the Engine" section.
Become familiar with the following information:
Types of the alarm and shutoff controls
Locations of the alarm and shutoff controls
Conditions which cause each control to function
Resetting procedure that is required before starting the engineOn G3300 Engines, protective devices are available for the following conditions:
Low oil pressure
High coolant temperature
Overspeed
Low coolant levelFurther protection is supplied by an emergency stop button.Three basic protection systems are available:
Self-powered shutoff
Automatic start/stop system
Customer supplied shutoffNote: For an energize-to-shutoff system, the gas shutoff valve must be energized to shut off gas to the engine. For an energize-to-run system, the gas shutoff valve must be energized in order to supply gas to the engine.Power for the self-powered system is supplied by the magneto. The self-powered system can be used with an air starting motor or an electric starting motor. An energize-to-shutoff gas valve and an instrument panel are required for this system.Power for the automatic start/stop system is supplied by an external 24 volt electrical source. The automatic start/stop system can be used with an air starting motor or an electric starting motor. An energize-to-run gas valve and one of these controls are required:
Automatic start/stop switchgear
Engine Control LogicFor the customer supplied shutoff system, the customer must supply all of the wiring and the shutoffs. This includes the emergency stop button and wiring.The features of the shutoff systems are listed in Table 1.
Table 1
G3300 Engine Protective Systems    
Item     Type of System    
Self-Powered Automatic Start/Stop     Customer Supplied (1)    
High coolant temperature     Yes     Yes     Yes    
Low oil pressure     Yes     Yes     Yes    
Overspeed     No (2)     Yes     Yes    
High inlet manifold air temperature     No     No     Yes (3)    
High aftercooler water temperature     No     No     Yes (3)    
Emergency stop     Yes     Yes     Yes    
( 1 ) The customer is responsible for supplying the shutoffs and the wiring.
( 2 ) Overspeed protection is available as an option.
( 3 ) The customer is responsible for supplying the protection for either high inlet manifold temperature or high aftercooler water temperature.Sensing Devices
The sensing devices that are described in this section are typical. The devices may be in different locations for different applications. Also, different applications may have different devices.Engines that use different generator set control panels will have different sensing devices.
Illustration 1 g00788382
(1) Speed sensor (2) Overspeed contactor (3) Air temperature switch (aftercooler) (4) Coolant temperature switch (5) Oil lineOverspeed
Speed sensor (1) (Illustration 1) helps to monitor the engine rpm. The speed sensor senses the motion of the flywheel ring gear. The speed sensor is used with a tachometer in order to display the engine rpm.The speed sensor can also be used with an electrical overspeed switch. An external power source of 24 volts DC is required.
Illustration 2 g00520644
Overspeed switchThe overspeed switch is mounted in the junction box. The recommended setpoint is 110 percent of the rated rpm. If an overspeed occurs, the "RESET" button on the switch must be reset before the engine can be started.The switch also has a "VERIFY" button. The button enables the operation of the switch to be tested at 75 percent of the rated rpm.Overspeed contactor (2) (Illustration 1) can be installed behind the magneto on the tachometer drive. The overspeed contactor is an mechanical device. Excessive engine rpm activates the contactor with centrifugal force.Temperature
Air temperature switch (3) (Illustration 1) for the aftercooler is installed in the housing of the aftercooler. The shutoff is supplied by the customer.Coolant temperature switch (4) (Illustration 1) is located next to the housing for the water temperature regulator. An excessive water temperature will activate a shutdown. The setpoint that is recommended for a high coolant temperature shutdown is 104 °C (220 °F).Oil Pressure
Oil lines (5) (Illustration 1) for sending oil pressure can be located in various places on the side of the engine block. The oil lines are connected to the bearing oil gallery. The oil lines can be connected to these different components:
Instrument panel
Junction box
Oil pressure switchLow oil pressure will activate a shutoff. The recommended setpoint for low oil pressure is 55 kPa (8 psi).Coolant Level