Systems Operation

Usage:

Operation

MARINE TRANSMISSION CUTAWAY

1. Oil pump.

2. Top shaft (input).

3. Pinion gears.

4. A head clutch (discs and plates).

5. Dump valve (for astern clutch).

6. Flexible connector (to engine flywheel).

7. Astern clutch (discs and plates).

8. Output shaft.

9. Bottom shaft.

10. Driven gears.

11. Dump valve (for ahead clutch).

The Marine transmission has a flexible connector (6) on top (input) shaft (2). Drive pinions (3) and driven gears (10) make a reduction in speed (rpm) so output shaft (8) from the transmission, turns slower than the speed (rpm) of the engine.

The flexible connector (6) has a spider with gear teeth on the diameter of the spider. The spider is on the top (input) shaft of the transmission. Another part of the flexible connector is a ring with gear teeth in the bore of the ring. The ring is on the engine flywheel. The flexible parts are the rubber blocks between the teeth on the spider and the teeth in the ring. The engine turns the flywheel and ring, the teeth in the ring push on the rubber blocks. The rubber blocks push the teeth on the spider which turns the spider and the top shaft of the transmission.

Back to back hydraulically activated clutches (4) and (7) operate the forward and reverse drives. A control valve directs the flow of oil to either of the clutches for forward or reverse operation. The valve is operated by a lever which can be manually or remotely controlled.

The oil pump (1) is connected to the end of top shaft (2) and turns at the same speed (rpm) as the engine. The oil for the pump is in the sump of the transmission. The oil from the pump is both for lubrication and is the supply of pressure oil that can activate either the ahead or the astern clutch.

NOTE: The reference to the clutches, is the astern clutch (reverse motion) and the ahead clutch (forward motion of the vessel when the propeller has a right hand pitch).

The astern clutch (front) section engages the three gear drive section in the marine gear which rotates the propeller shaft in the same direction of rotation as the engine. The ahead clutch (rear) section engages the two gear section which reverses the direction of propeller shaft rotation.

The direction of flywheel rotation for a standard engine is counterclockwise, when viewed from the flywheel end of the engine. With a right hand propeller, the ahead clutch (rear) section is engaged to produce ahead motion.

MARINE GEAR SCHEMATIC (Ahead Clutch Section Engaged)
4. Ahead clutch. 7. Astern clutch.

Hydraulic System

NOTE: In the information that follows the clutch rear section will be referred to as the "ahead clutch" and the clutch front section will be referred to as the "astern clutch."

Oil pump (1) supplies the hydraulic oil to the control valve. The control valve positions, AHEAD and REVERSE, direct the pressure oil to engage eithr ahead clutch (4) or astern clutch (7). Moving the control valve to the AHEAD position directs the hydraulic pressure oil through the oil passage around the tube assembly in the hollow center of top shaft (2). The pressure oil through the shaft flows through a passage in the spider assembly, and a passage in the clutch ring, to dump valve (11).

DUMP VALVE
12. Plunger (removed from body).

DUMP VALVE OPERATION (Clutch Engaged Position)
12. Plunger (forced inward). 13. Passage (to clutch piston). 14. Passage (pressure oil inlet).

The pressure oil in the dump valve passage forces plunger (12), that was held out by the centrifugal force of the rotating clutches, inward (down in the illustration). The down position of plunger (12) allows the pressure oil to flow through valve passage (13) which leads directly to the piston in ahead clutch (4). The pressure oil moves and holds the piston against the plates of ahead clutch (4), which engages the clutch.

DUMP VALVE (Clutch Disengaged Position)
12. Plunger (held out by centrifugal force). 13. Passage (to clutch piston). 15. Dump passage.

Movement of the control valve to the REVERSE position directs the hydraulic pressure oil through the tube assembly in top shaft (2), through the hydraulic passage in the spider assembly which leads to the (not shown in the cutaway) astern clutch dump valve (5). The valve directs the pressure oil to the astern clutch piston which engages astern clutch (7). Dump valves (5 and 11) are identical and operate in the same manner to either engage or disengage a clutch.

When the control valve is moved to NEUTRAL position, the pressure oil is no longer directed to a clutch. With no oil pressure to hold plunger (12) inward, the centrifugal force of the rotating clutches moves plungers (12) out. With the plunger out, oil passage (13) to a clutch engaging piston is open to dump passage (15). As the oil from the piston dumps, springs in the piston and cylinder assembly move the piston away from the clutch plates and the clutch disengages.

Control Valve

NEUTRAL Position

The control valve is on the right side of the marine transmission. All of the oil from the pump, when the engine is running, goes into the control valve. The lever on the control valve has three positions which are: AHEAD (forward), ASTERN (reverse) and NEUTRAL.

CONTROL VALVE IN NEUTRAL POSITION (Engine Running)
1. Control valve body. 2. Selector spool. 3. Springs (relief valve). 4. Outlet passage (to oil cooler). 5. Inlet passage (from filter and pump). 6. Relief valve. 7. Poppet.

The NEUTRAL position of the control lever keeps selector spool (2) in a position where the pump oil through inlet passage (5), and a passage in valve body (1), goes to a chamber with no outlet to the clutches. The pump oil also goes through a passage in relief valve (6) thru orifice in dampening poppet (7). With no outlet for the pump oil in the control valve the pressure of the pump oil increases. Pump oil pressure of 35 ± 5 psi (240 ± 35 kPa) opens relief valve (6) since the force in the dampening poppet (7) chamber of this valve (6) is greater than force of springs (3). As relief valve (6) opens pump oil goes thru outlet passage (4) thru the oil cooler and thru the lubricant passages in the transmission.

AHEAD Position

The AHEAD (forward) position of the control lever keeps selector spool (2), in a position where the pump oil through inlet passage (5), and a passage in valve body (1), goes through passage (16) to the ahead clutch. The pressure of the pump oil must increase to engage the clutch. The pump oil in passage (16) also moves ball (15), goes into check valve (11) and moves the check valve against stop (9). The pump oil is metered gradually thru the check valve orifice and into load piston (8) cavity. Pump oil flow thru passage (16) to ahead clutch fills the clutch piston and pressure increases to 35 ± 5 psi (240 ± 35 kPa). Relief valve (6) opens allowing oil to flow thru passage (4) to oil cooler and transmission lubrication. Pump oil continues to flow thru orifices (10) into flange end of load piston (8). Pressure increases on load piston (8) and forces the load piston (8) to move against springs (3) which increases force on relief valve (6). The gradual flow of oil metered thru check valve (11) gradually moves load piston (8) which gradually increases the pressure setting of relief valve (6) thus modulating the engagement of the ahead clutch. When movement of load piston (8) is stopped against bottom of counterbore in body (1), relief valve pressure is at 272 ± 8 psi (1870 ± 55 kPa) and ahead clutch is now fully engaged.

CONTROL VALVE IN AHEAD POSITION
1. Control valve body. 2. Selector spool. 3. Springs (relief valve). 4. Outlet passage (to oil cooler). 5. Inlet passage (from filter and pump). 6. Relief valve. 8. Load piston. 9. Stop. 10. Orifices (three). 11. Check valve. 12. Drain outlet (for oil to transmission housing). 13. Drain outlet (for oil to transmission housing). 14. Passage (for astern clutch). 15. Bail. 16. Passage (for ahead clutch). 17. Drain outlet (for oil to transmission housing).

POWER TRANSMISSION-AHEAD CLUTCH ENGAGED
18. Reverse idler gear. 19. Ahead clutch drive gear shaft. 20. Astern clutch driven gear shaft. 21. Planetary reduction gears. 22. Output propeller shaft.

ASTERN Position

The control valve operates the same in astern position as previously described for ahead position except:

1. Pump oil flow goes thru passage (14) to astern clutch instead of passage (16) to ahead clutch.

2. Ball (15) is seated in the opposite direction as shown for ahead position to direct oil from the astern clutch to check valve (11).

CONTROL VALVE IN ASTERN POSITION
1. Control valve body. 2. Selector spool. 3. Springs (relief valve). 4. Outlet passage (to oil cooler). 5. Inlet passage (from filter and pump). 6. Relief valve. 8. Load piston. 9. Stop. 10. Orifices (three). 11. Check valve. 12. Drain outlet (for oil to transmission housing). 13. Drain outlet (for oil to transmission housing). 14. Passage (for astern clutch). 15. Ball. 16. Passage (for ahead clutch). 17. Drain outlet (for oil to transmission housing).

POWER TRANSMISSION-ASTERN CLUTCH ENGAGED
18. Reverse idler gear. 19. Ahead clutch driven gear shaft. 20. Astern clutch driven gear shaft. 21. Planetary reduction gears. 22. Output propeller shaft.

Cooling System

The oil cooler is mounted on the right side of the marine gear housing. The oil temperature controlled bypass valve (3) controls the flow of lubricating oil through oil cooler (5).

When the temperature of the lubricating oil is below 150° F (65° C), bypass valve (3) is open. Lubricating oil from the control valve, through oil line (6), flows through bypass pipes (4) and through the open bypass valve directly into the oil manifold in the marine gear housing.

When lubricating oil temperature increases to approximately 150° F (65° C), bypass valve (3) starts to close and some of the lubricating oil flows through oil cooler (5). The bypass valve is completely closed when the lubricating oil temperature reaches 160° F (71° C). All of the oil from the control valve flows through oil cooler (5) and into the oil manifold in the marine gear housing.

OIL COOLER GROUP
1. Oil temperature gauge. 2. Oil temperature sensing switch. 3. Oil temperature controlled bypass valve. 4. Cooler bypass pipes. 5. Oil cooler. 6. Oil line to control valve.

Oil temperature sensing switch (2) is an electric switch that can be connected to some type of alarm which can be mounted at any distance from the marine gear. High temperature oil will close the switch and actuate the alarm.

Lubrication

The marine gear requires the same lubricant recommended for the engine. The gear-type oil pump (6) is driven by the top shaft (4) and is mounted on the rear of the marine gear. The oil pump draws oil from the sump in the bottom of the gear housing, through magnetic strainer (2), and pumps the oil through oil filter (1). All of the oil from the pump flows through the oil filter unless the filter is contaminated and the restriction through the filter is too high. If this should occur, the pressure oil from the pump will open the filter bypass valve.

OIL LINES FROM MANIFOLD
3. Control valve. 4. Top shaft. 5. Oil manifold (passage in gear housing).

The oil from the filter flows through an oil manifold to the control valve (3). Most of the filtered oil from the pump flows through the control valve, through an oil cooler (not shown in the schematic) and into an oil manifold (5) passage in the upper right side of the gear housing. Separate oil lines connected to fittings in the oil manifold distribute pressure oil to all bearings (8). Lower shaft rear roller bearing (12) is splash oil lubricated.

Oil line (7) carries pressure oil from manifold (5) to the planetary reduction section to lubricate thrust bearings (10) and planet gears (11).

Lubricating oil flows around top shaft (4) to supply the oil to cool and lubricate the ahead and astern clutch shaft bearings (9) and the clutch plates.

The main housing gears are splash lubricated by the meshing lower shaft gears which rotate in a controlled level of lubrication oil.

NOTE: The oil pump supplies lubrication oil to the marine gear when the engine is operating. If the vessel is to be towed with the engine stopped, secure the propeller shaft to keep it from rotating the gears and shafts in the marine gear.

LUBRICATING OIL SYSTEM-SCHEMATIC