Testing And Adjusting


Clutch Hydraulic System

When testing the hydraulic system the lubricating oil should be near the normal operating temperature of between 150 to 160° F (65 to 71° C).

A good recommendation to follow is to install a new element in the oil filter housing before a hydraulic pressure test is to be made.

There is no adjustment for either the ahead or astern clutch. If a clutch does not engage or keep engaged when the control is in either the AHEAD (forward) or ASTERN (reverse) position, the hydraulic pump is damaged or the clutch discs are badly worn.

Operation Test

To test the clutch engagement and lubricating oil system pressure, it is advisable to install a new; oil filter element.

With the engine stopped, remove the plug from the control valve and install a 5M5317 Reducing Bushing in the tee. Install a 5S4648 Hose Assembly with an 8M2886 Pressure Gauge (0 to 600 psi) in the reducing bushing and tee.

Start the engine and run it long enough to get the temperature of the oil, in the marine transmission, to approximately 150° F (65° C). Oil pressures are to be as shown in chart.

Operate the engine and observe the reading on the gauge when the control lever is moved to either the FORWARD or REVERSE position. The clutch engaged pressure reading should be 240 to 260 psi (1655 to 1790 kPa) in both positions. With the control lever in NEUTRAL position the lubricating oil system pressure should be a minimum of 55 psi (380 kPa).


If the oil pump is in satisfactory condition and it is necessary to adjust the clutch engaging pressure, spacers (1) located under springs (2) in relief valve (3), can be added to increase, or removed to decrease, clutch engagement oil pressure.

Remove the cover from the bottom of the control valve. Relief valve (3) and springs (1) can fall when the cover is removed. Add spacers (2), in relief valve (3) under springs (1) to increase the pressure of the oil to engage a clutch. Remove spacers (2) if the pressure reading on the gauge was too high.

Put springs (1), relief valve (3) with spacers (2) into the control valve and install the cover.

1. Springs. 2. Spacers. 3. Relief valve.

Test the oil pressure again. When the pressure reading is correct stop the engine and remove the hose assembly and reducing bushing. Install the plug in the tee on the control valve.

Vessel Either Pulled Or Pushed

Keep the propeller stopped when the vessel is either pulled or pushed with a stopped engine. The motion of the vessel can turn the propeller and there is no lubrication for the bearings and gears and clutch discs that turn with the propeller.

Marine Transmission Alignment

See the CATERPILLAR MARINE ENGINE APPLICATION AND INSTALLATION GUIDE for the correct alignment procedure. Also see Special Instruction Form No. SEHS7654 for alignment general instructions.

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