Engine Coolant Temperature Sensor - MerCruiser 305 CID (5.0L) Service Manual

SUPPLEMENT TO SERVICE MANUAL NUMBER 24
CLEANING AND INSPECTION
1. Clean the exterior of the ECM with a dry cloth being careful to avoid contact with
connector pins.
2. Inspect outer surfaces for any obvious damage
3. Visually inspect electrical pins at both ends of ECM for straightness and corrosion.
4. Visually inspect J1 and J2 connectors on the wiring harness for corrosion and terminals
that may have backed of the harness.
NOTE: The ECM is a sealed electrical component. If a Code 51 check has shown it to be
defective, replace the unit with another ECM having the same part number as the original.
INSTALLATION
1. Mount new ECM to electrical bracket using screws and washers.
2. Connect J1 and J2 electrical connectors to the ECM. DO NOT touch connector pins
when installing.

Engine Coolant Temperature Sensor

REMOVAL
NOTE: Handle the ECT sensor carefully. Damage to it will affect operation of the system.
1. Disconnect electrical connector at Engine Coolant Temperature (ECT) sensor.
2. Remove ECT sensor from thermostat housing.
CLEANING AND INSPECTION
1. Clean with a dry cloth, removing any excess sealant from the base threads.
2. Look for evidence of any physical damage to base or connector surfaces of the ECT
sensor.
INSTALLATION
1. Install ECT sensor in thermostat housing. Tighten hand tight plus 2-1/2 turns maximum.
2. Connect electrical connector to ECT sensor.
90-861327000 JULY 2000
b
a - Thermostat Housing
b - Engine Coolant Temperature (ECT) Sensor
FUEL INJECTION DISASSEMBLY AND REASSEMBLY
a
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