ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – 008-103   Sea Water System Diagnostics

NOTE: This procedure is for marine applications only. Refer to Procedure 008-020 for engine coolant diagnostic procedures.

This is a typical sea water cooling system. For more engine specific system identification, refer to Procedure 200-003.

1. Grate-type strainer located on the bottom of the boat hull
2. Vessel bottom/hull
3. Sea water inlet valve
4. Hose
5. Sea water strainer

6. Sea water pump
7. Fuel cooler
8. Aftercooler
9. Marine gear oil cooler
10. Heat exchanger
11. Sea water outlet.

Locate and verify that the sea water inlet valve is in the full open position. If it is closed or partially closed, open the valve and recheck the engine temperature.

Inspect the sea water strainer for foreign objects that could restrict the water flow.

Some strainers have clear covers for easy inspection. If the strainer has to be opened for inspection, refer to Procedure 008-067.

If the engine was in operation with the sea water system highly restricted due to a closed sea water inlet valve or a clogged sea water strainer, the sea water impeller must be inspected for damage.

If the hours in service of the sea water impeller is unknown, then inspection of the sea water impeller is advisable. Refer to Procedure 008-057.

If the engine continues to overheat, perform the following procedures. If the engine does not overheat at the dock, perform a sea trial and check for overheating under way.

Attach a vacuum gauge to the inlet side of the sea water pump.

Start the engine.

Record the sea water inlet restriction from low idle to rated speed at 500 rpm increments. This test can be conducted while the vessel is at the dock and not in gear or underway.

Refer to Procedure 018-018 for Marine engine specifications.

If the sea water inlet restriction is above specification, the source of the restriction must be found. Troubleshooting and repair of excessive sea water restriction is a boat manufacturer or boat owner responsibility. Refer to the vessel’s OEM service manual. If the inlet restriction is within the specification and the complaint can not be verified at the dock, the test must be repeated underway.

Areas to inspect for restriction are a plugged sea water strainer, sea water valve not fully open, defective hose liner in a supply hose, or debris in the inlet hose.

If the sea water inlet restriction readings fluctuate during the test, inspect the sea water supply for leaks or air intrusion. Troubleshooting and repair of excessive sea water restriction is a boat manufacturer or boat owner responsibility. Refer to the vessel’s OEM service manual. Troubleshooting and repair for sea water aeration is not covered under Cummins warranty.

Areas to inspect for a source of air are the sea water strainer inspection cover seal, sea water valve shaft seal packing, or loose hose clamps.

It is possible that aeration (gauge fluctuation) will only
occur while the vessel is underway due to the introduction of air. Refer to the vessel’s OEM service manual.

Areas to inspect for a source of aeration are water inlet scoop installed backwards, incorrect water inlet scoop, or water inlet location on the hull in aerated water flow.

Attach a pressure gauge to the outlet side of the sea water pump to check pump outlet pressure.

Start the engine and record the sea water outlet pressure from low idle to rated speed at 500 rpm increments. This test can be conducted while the vessel is at dock and not in gear or underway.

Refer to Procedure 018-018 for Marine engine specifications.

If the sea water pump outlet pressure is within specifications, see the Temperature Differential Test step in this procedure.

If sea water pressure is not present, check the pump for damage. Refer to Procedure 008-057.

If the sea water pump outlet pressure is above the maximum specification test the individual sea water system components for excessive pressure drop as described in the Pressure Differential Test step.

Refer to Procedure 018-018 for Marine engine specifications.

Check the sea water pressure at the inlet side of the aftercooler at the rated rpm. Record the reading. If the pressure drop between the sea water pump outlet and the aftercooler inlet exceeds the maximum specification, check or replace the fuel cooler.

Refer to Procedure 018-018 for Marine engine specifications.

If the pressure drop is within specification, check the sea water pressure at the discharge side of the aftercooler outlet. Record the reading.

If the pressure drop between the inlet side of the aftercooler exceeds the maximum, check for blockage in the lower cap area of the aftercooler. Clean or replace if necessary. Refer to Procedure 010-005.

Shut off the sea water supply valve and remove the lower aftercooler sea water supply hose. Clean the debris from the aftercooler and cap. Remove the upper sea water hose and back flush the system.

Refer to Procedure 018-018 for Marine engine specifications.

If the pressure drop between the inlet side of the aftercooler and the outlet side of the aftercooler is within specification, attach the pressure gauge to the gear oil cooler drain plug located on the outlet and check for pressure drop across the gear oil cooler.

If the pressure drop between the inlet side (1) and the outlet side
(2) of the gear cooler is greater than the maximum specification, check for blockage in the gear cooler. Clean or replace if necessary. Refer to Procedure 008-041.

Refer to Procedure 018-018 for Marine engine specifications.

If the pressure drop in the gear oil cooler is within specification, test the pressure drop across the engine heat exchanger.

Fabricate a sea water test tool by using a 38 mm [1-1/2 in] pipe with a fitting in the center to connect a pressure gauge.

Install the fabricated test tool between the outlet side of the heat exchanger and the exhaust elbow. Check the pressure drop across the heat exchanger.

If the pressure drop is greater than the maximum specification, check for blockage in the heat exchanger. Clean or replace if necessary.

Refer to Procedure 018-018 for Marine engine specifications.

If the pressure drop across the heat exchanger is within specification, determine the pressure drop across the exhaust elbow (diffuser). This is done by subtracting the heat exchanger outlet pressure form the sea water pump outlet pressure. If this pressure exceeds the maximum specification, check for blockage in the exhaust elbow (diffuser) and exhaust system of the vessel. Clean or replace if necessary.

Refer to Procedure 018-018 for Marine engine specifications.

Some vessels are equipped with a sea water bypass valve to divert sea water flow from the exhaust elbow. If the valve is adjusted to the lowest system pressure, be sure the exhaust piping does not overheat under all operating conditions.

Check the sea water pressure at the inlet side of the aftercooler at the rated rpm.

Record the reading. Refer to Procedure 018-018
for marine engine specifications.

If the pressure drop between the sea water pump outlet and the aftercooler inlet exceeds the maximum specification, check for blockage or damage to the marine gear oil/fuel cooler.

Shut off the sea water supply valve. Refer to the OEM service manual.

Remove the marine gear oil/fuel cooler inlet and outlet hoses. Refer to Procedure 008-129.

Clean the debris from the inlet side. Use a hose and back flush the cooler. Refer to Procedure 008-129.

If the pressure drop is within specification, check the sea water pressure at the discharge side of the aftercooler outlet. Record the reading.

If the pressure drop between the inlet side of the aftercooler exceeds the maximum, check for blockage in the lower cap area of the aftercooler. Refer to Procedure 018-018 for marine engine specifications.

Clean or replace if necessary. Refer to Procedure 010-005.

If the pressure drop between the inlet side of the aftercooler and the outlet side of the aftercooler is within specification, check for pressure drop across the engine heat exchanger.

Fabricate a sea water test tool by using a 38 mm [1-1/2 in] pipe with a fitting in the center to connect a pressure gauge.

Install the fabricated test tool between the outlet side of the heat exchanger and the exhaust elbow.

Check the pressure drop across the heat exchanger. Refer to Procedure 018-018 for marine specifications.

If the pressure drop is greater than the maximum specification, check for blockage in the heat exchanger.

Clean or replace the heat exchanger if necessary. Refer to Procedure 008-053.

If the pressure drop across the heat exchanger is within specification, determine the pressure drop across the exhaust elbow (diffuser). This is done by subtracting the heat exchanger outlet pressure from the sea water pump outlet pressure. Refer to Procedure 018-018
for marine specifications.

If the pressure exceeds the maximum specification, check for blockage in the exhaust elbow (diffuser) and exhaust system of the vessel.

Clean or replace the elbow if necessary.

Some vessels are equipped with a sea water bypass valve to divert sea water flow from the exhaust elbow. If the valve is adjusted to the lowest system pressure, be sure the exhaust piping does not overheat under all operating conditions.

Fabricate a sea water test tool by using a 38 mm [1-1/2 in] pipe with a fitting in the center to connect a temperature probe.

Install the sea water test tool with a temperature probe between the outlet side of the heat exchanger and the exhaust elbow (1). Operate the engine at rated rpm and load and record the temperature.

Install the temperature probe in the outlet side of the aftercooler
(1). Operate the engine at the rated rpm and load and record the temperature. If the temperature difference between the aftercooler outlet and the engine heat exchanger outlet is greater than 20°C [40°F], check the sea water pump for water flow problems. Refer to Procedure 008-057.

If the sea water temperature difference is less than 3°C [5°F], check the heat exchanger for possible plating to the heat exchanger core. Excessive plating or coating to the inside or outside of the cooling tubes will effect the efficiency of the heat exchanger. Refer to Procedure 008-053.

Fabricate a sea water test tool by using a 38 mm [1-1/2 in] pipe with a fitting in the center to connect a temperature gauge.

Install the fabricated test tool between the outlet side of the heat exchanger and the exhaust elbow.

Operate the engine at rated rpm and load and record the temperature.

Refer to Procedure 018-018 for marine specifications.

Install the temperature probe in the outlet side of the marine gear oil/fuel cooler. Operate the engine at the rated rpm and load.

Record the reading. Refer to Procedure 018-018
for marine engine specifications.

Install the temperature probe in the outlet side of the aftercooler. Operate the engine at the rated rpm and load.

Record the reading. Refer to Procedure 018-018. for marine engine specifications.

If the temperature difference between the marine gear oil/fuel cooler outlet and heat exchanger outlet, or the aftercooler outlet and the marine gear oil/fuel cooler outlet is greater than 20°C [40°F], check the sea water pump for water flow problems. Refer to Procedure 008-057.

If the sea water temperature difference is less than 3°C [5°F], check the heat exchanger and marine gear oil/fuel cooler for possible plating to the cores. Excessive plating or coating to the inside or outside of the cooling tubes will effect the efficiency.