7261 MARINE GEAR Caterpillar

Testing And Adjusting


Clutch Actuating Pressure

A clutch that will not engage can be caused by either a loss in clutch hydraulic pressure (oil pump output) or by a defective clutch. The clutch hydraulic actuating pressure should be tested first.

Remove the plug from the oil pressure test location on the selector valve and install a 5S4648 hose, 8M2886 Gauge (0-600 PSI) and the necessary fittings.

With the selector lever in NEUTRAL and the engine operating at full load RPM, the gauge should indicate 70 ± 10 PSI (4,9 ± 0,7 kg/cm2).


The gauge should indicate 290 ± 10 PSI (20,4 ± 0,7 kg/cm2), clutch hydraulic actuating pressure, with the selector lever moved to engage either the the ahead or astern clutch.

Come-Home Feature

If the marine transmission loses oil pressure, and if there is no other means for returning to port, the come-home feature can be used. This features allows a clutch to be mechanically engaged by tightening bolts or setscrews which compress the clutch pack. The clutch pack nearest the engine flywheel housing cannot be engaged with bolts.


Use the come-home feature only in an emergency. If the marine transmission lubricating oi pressure is lost, travel with extreme care and at minimum engine speed to avoid damaging the bearings.

1. The engine must be warm. If necessary, start and idle engine until it is warm.

2. Stop the engine.

3. Remove the access cover from the top of the marine gear housing.

4. Mechanically engage the rear most clutch in the marine gear as described below.

5. Install two 5/8-11, 1.50 in. (38.1 mm) bolts opposite each other in the tapped holes in the back plate of the clutch assembly. Tighten the bolts evenly to a torque of 130 to 150 lb. ft. (18.0 to 20.7 mkg). Do not tighten the bolts too tight.

NOTE: On later marine gears use the following procedure: Install three 3/8-16, 1.50 in. (38.1 mm) bolts in the three tapped holes in the back plate of the clutch assembly. Tighten the bolts evenly to a torque of 32 ± 5 lb. ft. (4.4 ± 0.7 mkg).


6. Install the access cover.

7. Start the engine.


The starter motor will be turning the diesel engine, marine gear, propeller shaft, and propeller while cranking. Avoid creating excessive heat in the starter by overcranking. Damage can result.

8. Check the marine gear oil level. Maintain oil at the full mark on the dipstick.

9. After starting, travel with caution: usually at minimum speed.

10. To stop the vessel, stop the engine. Remove the bolts engaging the clutch when the engine is stopped.

11. Upon reaching port, disassemble and inspect the clutch plates for warpage and cracking: Damage can occur by having been mechanically engaged. Under severe operating conditions, the marine gear should be disassembled and all bearings inspected.

Fabricated Tools

The disassembly and assembly of this marine gear can be facilitated by the use of the following fabricated tools:

FT836 Bearing Cap


After the top shaft assembly has been replaced in the housing, the FT836 Bearing Cap should be used to properly seat 6L5438 Bearing Assembly in its bore. When the 6L5438 Bearing is properly seated, the two remaining bearings will also be seated correctly.

FT840 Retaining Brackets


When installing the top shaft and clutch assembly, two FT840 Retaining Brackets should be used to prevent the top shaft from sliding out of the clutch pack. The brackets can also be used while disassembling the clutch.

FT841 Clamping Tool


The FT841 Clamping Tool provides a quick easy method for compressing piston springs when installing the retaining rings in the ahead-astern clutch.

FT850 Locking Bracket


The FT850 Locking Bracket provides a secure method of pulling the lower shaft loose from the 4L1257 Ahead Driven Gear. This bracket provides an adjustable spacer between the gear and the compartment wall. Thus, the bracket distributes the load over a wider area and prevents damage to the compartment wall when the puller is utilized.

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