3H9-03200-1 Tohatsu CARBURETOR ASSY

Illustration 1 g00281646
Air Inlet And Exhaust System (1) Exhaust manifold. (2) Aftercooler. (3) Engine cylinder. (4) Air inlet. (5) Turbocharger compressor wheel. (6) Turbocharger turbine wheel. (7) Exhaust outlet.Clean inlet air from the air cleaners is pulled through air inlet (4) into the turbocharger compressor by the turbocharger compressor wheel (5). The rotation of the turbocharger compressor wheel causes the air to compress. The rotation of the turbocharger compressor wheel then forces the air through a tube to aftercooler (2). The aftercooler lowers the temperature of the compressed air before the air goes into the inlet chambers in each cylinder head. This cooled and compressed air fills the inlet chambers in the cylinder heads. Air flows from the inlet chambers in the cylinder heads. Air flow from the inlet chamber into the cylinder is controlled by the inlet valves.There are two inlet valves and two exhaust valves for each cylinder. Make reference to Valve System Components. The inlet valves open when the piston moves down on the inlet stroke. The cooled, compressed air is pulled into the cylinder from the inlet chamber.The inlet valves close and the piston starts to move up on the compression stroke. When the piston is near the top of the compression stroke, fuel is injected into the cylinder. The fuel mixes with the air and combustion starts. The force of the combustion pushes the piston downward on the power stroke. When the piston moves upward the piston is on the exhaust stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into exhaust manifold (1). After the piston makes the exhaust stroke, the exhaust valves close and the cycle starts again.Exhaust gases from the exhaust manifold go into the turbine side of the turbocharger. The exhaust gases cause the turbocharger turbine wheel (6) to turn. The turbine wheel is connected to the shaft that drives the turbocharger compressor wheel (5). The exhaust gases exit through the exhaust outlet (7) .Aftercooler
The aftercooler is located at the center of the vee. The aftercooler has a coolant charged core assembly (assemblies). Coolant from the water pump flows through a pipe into the aftercooler. Coolant then flows through the core assembly (assemblies). Coolant flows back out the aftercooler through a different pipe.There is a connector (tube) that connects the bottom rear of each core assembly to the cylinder block. This connector is used in order to drain the aftercooler when the coolant is drained from the engine. Inlet air from the compressor side of the turbochargers flows into the aftercooler through pipes. The air then passes through the fins of the core assembly (assemblies) which lowers the temperature. The cooler air flows out of the bottom of the aftercooler and into the air chamber. The air flows through the elbows to the inlet ports (passages) in the cylinder heads.One drain plug is located between the No. 1 and 3 cylinder heads. Another plug is located between the last two cylinder heads on the left side of the engine. These plugs can be removed to check for water or coolant in the aftercooler air chamber.Turbochargers
The 3508 and the 3512 have two turbochargers that are used on the rear of the engine. The 3516 has four turbochargers which are mounted in the center of the engine. The turbine side of each turbocharger is connected to its respective exhaust manifold. The compressor side of each turbocharger is connected by pipes to the aftercooler housing. The turbocharger is supported by the central exhaust elbow.
Illustration 2 g00322583
Turbochargers (Typical Example) (1) Turbocharger. (2) Oil drain line. (3) Oil supply line.
Illustration 3 g00307853
Turbocharger (Typical Example) (4) Compressor wheel. (5) Bearing. (6) Oil inlet. (7) Bearing. (8) Turbine housing. (9) Turbine wheel. (10) Air inlet. (11) Oil outlet.The exhaust gases go into the exhaust inlet of the turbine housing. The gases push the blades of turbine wheel (9). The turbine wheel and the compressor wheel turn at speeds up to 60,000 rpm.Clean air from the air cleaners is pulled through the compressor housing air inlet (10) by the rotation of the compressor wheel (4). The action of the compressor wheel blades causes a compression of the inlet air. This compression gives the engine more power because the compression allows the engine to burn additional fuel with greater efficiency.The maximum speed of the turbocharger is controlled by the fuel setting, the height above sea level, and the inlet restriction.
If the fuel setting is higher than given in the TMI (Technical Marketing Information), there can be damage to engine or turbocharger parts. Damage will result when increased heat and/or friction due to the higher engine output goes beyond the engine cooling and lubrication systems abilities. A mechanic that has the proper training is the only one to make the adjustment of fuel setting and high idle rpm setting.
Bearing (5) and bearing (7) in the turbocharger use engine oil under pressure for lubrication. The oil is sent through the oil inlet line to oil inlet port (6). The oil then goes through passages in the center section for lubrication of the bearings. The oil goes out of oil outlet port (11) at the bottom. The oil then goes back to the flywheel housing through the drain line.Valve System Components
The valve system components control the flow of the inlet air and the exhaust gases into the cylinders and out of the cylinders during engine operation.The crankshaft gear drives the camshaft gears through idlers. Both camshafts must be timed to the crankshaft in order to get the correct relation between the piston and the valve movement.
Illustration 4 g00322585
Valve System Components (1) Rocker arm. (2) Bridge. (3) Rotocoil. (4) Valve spring. (5) Pushrod. (6) Lifter.The camshafts have three lobes for each cylinder. Two lobes operate the valves and one operates the unit injector.As each camshaft turns, the lobes on the camshaft cause the lifters (6) to move up and down. This movement causes the pushrods (5) to move the rocker arms (1). The movement of the rocker arm causes