Service Manual

ISB, ISBe and QSB (Common Rail [...] Sea Water System Diagnostics
Section 8 - Cooling System - Group 08 Page 8-115
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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.
Pressure Test
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.