Usage:
The 3N7478 Overspeed Contactor Group has a speed switch that will cause the engine to shutdown (stop running) if the engine has an overspeed condition (engine runs too fast). The 3N9595 Overspeed Contactor Group has a speed switch that is a dual speed switch [controls two separate speed conditions - one part of the switch will cause crank termination (the speed at which the starting motor pinion will disengage from the engine flywheel) and the other part of the speed switch will cause the engine to shutdown (stop running) if the engine has an overspeed condition (engine runs too fast)].
NOTE: The magnetic pick-up cannot be installed on a Marine Engine that does not have a No. 1 flywheel housing.
(1) To install the magnetic pick-up, remove plate (1) if the engine is so equipped. On engines that do not have plate (1), remove a plug (2) that has a 5/8"-18 UNF thread.
(2) For engines that have plate (1), install the new 3N8388 Plate (3) with the four S1594 Bolts and 3B4506 Lockwashers so hole (A), is in alignment with the teeth on the flywheel ring gear.
(3) Install magnetic pick-up (5), with locknut (4), in either the hole for plug (2) in flywheel housing (6) or in hole (A) in plate (3). Install the magnetic pick-up until the end comes in contact with teeth (7) on the flywheel ring gear.
(4) Loosen magnetic pick-up (5) 1/2 turn. This will give approximately .022"-.033" (0.55-0.83) clearance at location (B), between the end of the magnetic pick-up and the teeth on the flywheel ring gear. When clearance at location (B) is correct, tighten locknut (4) to a torque of 50 ± 10 lb. ft. (6.9 ± 1.4 mkg) (68.0 ± 13.6 N·m).
NOTE: The instructions that follow give one method to fasten speed switch (8) on the engine. If desired, it is permissible to fasten the speed switch in any location that has good access and is near the engine.
(5) For installation of the speed switch on the engine, fasten switch (8) to 3N7689 Plate (10) with four 3N7588 Mounts (9) and eight 4B2043 Nuts (11) with 3B4501 Lockwashers. Use the illustrations above as a guide according to engine model.
(6) For D330C, D333C, D334, D343, 3304, 3306, 3406 and 3408 Engines, remove two bolts from the engine oil pan and then fasten plate (10), with switch (8), to the engine oil pan (12). Use two 2P3204 Bolts (13) with 4B4278 Washers in the bolt holes for the bolts that were removed, to fasten bracket (10) in position.
(7) For D353 Engines, fasten plate (10), with switch (8), to the side of the cylinder block (14) at location (C), with two S1585 Bolts (15) and 3B4508 Lockwashers.
Electrical Connections
(1) Explanation of wiring diagram.
A - Oil Pressure Switch - Push button in to allow engine to start (run). After engine is running, engine oil pressure moves button to the run position.
B - Water Temperature Contactor
C - Magnetic Pick-Up - Clearance between end of magnetic pick-up (C) and teeth on ring gear of flywheel (D) must be .022"-.033" (0.55-0.83). Tighten magnetic pick-up locknut to 50 ± 10 lb. ft. (6.9 ± 1.4) (68.0 ± 13.6) after adjustment is correct.
D - Engine Flywheel
E - Verify (make sure of correct operation) - Make a temporary connection between terminals 1 and 2. This connection causes the electronic speed switch to activate and shutdown the engine at 75% of the overspeed (engine runs too fast) set point. On the earlier type of electronic speed switch, this connection causes the electronic speed switch to activate and shutdown the engine at 25% of the overspeed set point. NOTE: On the earlier type (25% verify) terminals 7 and 9 are marked with the wrong electrical code letters. Terminal 7 must be marked NO and terminal 9 must be marked NC for the correct electrical code.
F - Input Voltage (Voltage in) - Maximum voltage must not be more than 37V DC and minimum voltage must not be less than 8V DC.
G - Run-Overspeed Switch - After an overspeed shutdown, switch (G) must be moved to the RUN position before the engine can start (run). Shut off the power to the electronic overspeed switch before switch (G) is moved to the RUN position. Turn on power after switch (G) movement is complete.
H - Rack Solenoid
J - Diode Assembly - Used for suppression of arcing, for protection of the speed switch.
K - Pressure Delay Switch - This switch is used to turn power ON and OFF the electronic speed switch. The 3N8783 Pressure Delay Switch is normally used for this operation.
(2) If the engine is equipped with a Woodward 2301 Governor and a 3N6878 or 3N9596 Electronic Speed Switch, the magnetic pick-up that is used with the overspeed switch is the only magnetic pick-up that is needed. Connect the Woodward 2301 Governor to the overspeed switch as shown in the illustration. Connect the wiring at the governor according to the wiring instructions sent with the governor.
(3) If the engine is equipped with a Woodward 2301 Governor and a 3N9596 Speed Switch, connect the wiring as shown in the illustration above. Connect the wiring to the governor according to the wiring instructions included with the governor.
Check Of The Electronic Speed Switch For Correct Operation
(1) Remove cover (1). Make a temporary connection between terminals 1 and 2 of the speed switch.
NOTE: Some of the early 3N7478 Overspeed Contactor Groups have a speed switch that activates and stops the engine at 25% of the overspeed set point. A method of identification for these early 25% speed switches is to look at terminals 7 and 9. The electrical code letters for these terminals are wrong. Terminal 7 has the letters (NC) and terminal 9 has the letters (NO). Make a change to these two terminals so the letters for terminal 7 are (NO) and the letters for terminal 9 are (NC). After the change is made, put a mark on the speed switch to show the change to the terminals and also make a mark so it is known that it is a 25% speed switch. The speed switch in the 3N9595 Overspeed Contactor Group and in the later 3N7478 Overspeed Contactor Groups activate at 75% of the overspeed set point. The speed switch in each of these groups has an identification mark to show it is a 75% speed switch.
(2) Use one of the tool groups that follow to measure the speed of the engine: 4S6553 Engine Test Group, 1P5500 Portable Phototach Group or 5P2150 Engine Horsepower Meter.
(3) Run the engine. Look at the chart that follows. According to the engine full load speed, type of installation and the type of speed switch known to be on the engine (either 25% switch or 75% switch) the engine must stop at the test speed shown.
(4) If the speed switch does not stop the engine at the correct overspeed test rpm, remove screw (3), (5) or (6). Put a small screwdriver in the screw hole and use the procedure that follows:
a - On 3N6878 Speed Switch (2), turn adjustment screw at location (3) clockwise to increase or counterclockwise to decrease the rpm at which the engine will stop.
b - On 3N9596 Speed Switch (4), turn adjustment screw at location (5) [above the letters OS (overspeed)] clockwise to increase or counterclockwise to decrease the rpm at which the engine will stop.
c - On 3N9596 Speed Switch (4), turn adjustment screw at location (6) [above the letters CT (crank termination)] clockwise to increase or counterclockwise to decrease the rpm at which the starting motor pinion will disengage from the flywheel.