353-03221-0 Tohatsu FLOAT CHAMBER

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Schematic of the coolant flow for the jacket water and for the separate circuitJacket Water System
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Right side view (1) Tube for the coolant from the turbocharger and from the exhaust bypass valve to the water cooled exhaust manifold (2) Water cooled exhaust manifold (3) Water temperature regulator housing (4) Outlet for the water temperature regulator housing (5) Inlet for the jacket water pump (6) Tube for the coolant to the turbocharger and to the exhaust bypass valve (7) Bonnet for the outlet of the engine oil cooler (8) Bonnet for the inlet of the engine oil coolerThe jacket water pump is located on the right front side of the engine. The water pump has a gear that is driven by the front gear group. Coolant from the radiator or from the heat exchanger enters inlet (5). The rotation of the impeller in the jacket water pump pushes the coolant to bonnet (8) for the inlet of the engine oil cooler.The flow of coolant from the engine oil cooler is divided. Most of the coolant from bonnet (7) for the outlet of the engine oil cooler flows into the cylinder block.The remainder of the coolant flows through tube (6) in order to cool the turbocharger turbine housing and the exhaust bypass valve. Coolant from the turbocharger turbine housing and from the exhaust bypass valve flows through tube (1) to water cooled exhaust manifold (2) .The coolant inside the cylinder block flows around the cylinder liners. The water jacket is smaller near the top of the cylinder liners. This shelf causes the coolant to flow faster for better cooling of the cylinder liner. The coolant is pumped through the top deck of the cylinder block into the cylinder heads. The coolant flows through passages around the valves and around the exhaust gases in the cylinder head.The coolant exits the cylinder head through water cooled exhaust manifold (2) . The water cooled exhaust manifold directs the coolant to water temperature regulator housings (3). The engine has two water temperature regulators. The water temperature regulators control the direction of the coolant flow according to the coolant temperature.
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Front view (2) Water cooled exhaust manifold (3) Water temperature regulator housing (4) Outlet for the water temperature regulator housing (5) Inlet for the jacket water pump (9) Bypass tube When the coolant is cold, the water temperature regulator is closed. The coolant is routed through bypass tubes (9) to the jacket water pump. The coolant continues to circulate through the engine.When the coolant achieves normal operating temperature, the water temperature regulators open and coolant flow is divided. Most of the coolant exits outlet (4) from the top of the water temperature regulator housings in order to be cooled by the radiator or by the heat exchanger. The remainder of the coolant flows through bypass tubes (9) to the jacket water pump for recirculation. After the coolant is cooled by the radiator or by the heat exchanger, the coolant is routed to inlet (5) of the jacket water pump.Note: The water temperature regulators are necessary to maintain the correct engine temperature. If the water temperature regulators are not installed in the system, there is no mechanical control. Most of the coolant will take the path of least resistance through the bypass tube. This will cause the engine to overheat in hot weather. The small amount of coolant that goes through the radiator or through the heat exchanger in cold weather will not allow the engine to achieve normal operating temperatures. The water temperature regulators control the minimum temperature of the coolant. The radiator or the heat exchanger controls the maximum temperature of the coolant.The total system capacity depends on the amount of coolant in the cylinder block, the capacity of the piping, and of the radiator or heat exchanger.Separate Circuit
A separate cooling circuit is necessary for the aftercooler because the jacket water cannot provide the low coolant temperature that is necessary for cooling of the turbocharged air.
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Rear view (1) Aftercooler (2) Outlet from the aftercooler (3) Inlet of the auxiliary water pumpThe auxiliary water pump has a gear that is driven by the rear gear group. Coolant from the customer supplied radiator or the heat exchanger enters inlet (3). The rotation of the impeller in the auxiliary water pump pushes the coolant to aftercooler (1) .The coolant flows through the passages in the aftercooler. The air that is compressed and heated by the turbocharger exchanges heat with the coolant in the aftercooler. The coolant flows from the aftercooler through outlet (5) in order to circulate back to the customer supplied radiator or to the heat exchanger.The engine rating and the application determine the operating temperature of the aftercooler. The aftercooler can maintain the coolant at one of these temperatures:
32 °C (90 °F)
54 °C (130 °F)