ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – 008-014   Coolant Thermostat Housing

This procedure applies to QSL9 keel cooled engines only.

WARNING  Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.

WARNING  Coolant is toxic. Keep away from children and pets. If not reused, dispose of in accordance with local environmental regulations.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

CAUTION  Use caution when draining coolant that coolant is not spilled or drained into the bilge area. Do not pump the coolant overboard. If the coolant is not reused, it must be discarded in accordance with local environmental regulations.

• Disconnect the batteries. Refer to Procedure 013-009.
• Drain the engine coolant. Refer to Procedure 008-018.
• Disconnect the keel cooler inlet and outlet connections. Refer to the OEM service manual.
• Disconnect the coolant vent line from the thermostat housing. Refer to Procedure 008-017.
• Disconnect the thermostat housing coolant inlet and outlet hoses.

Remove the four thermostat housing mounting capscrews.

Remove the two clamps and the thermostat housing.

Remove the two vibration isolators.

The engine thermostat and thermostat seal must operate properly in order for the engine to operate in the most efficient heat range. Overheating or overcooling will shorten engine life.

Fabricate a test fixture to seal all of the water outlet connections except the outlet port to the keel cooler and the inlet port of the thermostat housing.

For the outlet port to the keel cooler (1), install a hose long enough to reach a remote, dry container used to collect water. Place the open end of the hose in the dry container.

Connect a water hose to the inlet port (2) of the thermostat housing capable of regulating 152 kPa [22 psi] of filtered tap water.

Apply 152 kPa [22 psi] of water pressure to the thermostat housing for one minute.

The maximum allowable leakage is 100 cc [3.4 fl oz] per minute.

If more than 100 cc [3.4 fl oz] of coolant is collected, the thermostat or thermostat seal is leaking and must be replaced. Refer to Procedure 008-016 to replace the thermostat seal.

Remove the three capscrews and hose connections from the ends of the thermostat housing.

Remove the o-rings from the ends of the housing.

Remove the keel cooler hose connections.

Remove the coolant vent fitting and pipe plugs from the housing.

Clean the parts with soap and water.

Dry with compressed air.

Inspect the components for cracks, nicks, or other damage.

Inspect the thermostat seal for damage. Replace the seal if damaged. Refer to Procedure 008-016.

Inspect the isolators for damage or cracks.

Replace any damaged parts.

Install the thermostat into the thermostat housing.

Install a new o-ring on the thermostat housing.

Install the water inlet connection and three mounting capscrews. Tighten the capscrews.

Install a new o-ring on the other end of the thermostat housing and the water outlet connection. Install the three capscrews and tighten.

Install the two pipe plugs and tighten.

Install the coolant vent line fitting. Tighten the fitting so it faces the thermostat housing inlet end.

Install the keel cooler inlet and outlet fittings. Refer to the OEM service manual.

Place the vibration isolators on top of the thermostat housing support bracket.

Install the thermostat housing onto the isolators using clamps and capscrews as shown.

Tighten the capscrews.

• Install the coolant inlet and outlet hoses.
• Install the coolant vent line. Refer to Procedure 008-017.
• Install the keel cooler inlet and outlet hoses. Refer to the OEM service manual.
• Fill the engine with coolant. Refer to Procedure 008-018.
• Connect the batteries. Refer to Procedure 013-009.

Operate the engine and check for leaks.