41089 Mercruiser SCREW

(1) Oil Pump <D3>The oil pump, of a gear type, is driven by the skew gear mounted on the camshaft.The oil pump cover serves also as the oil filter head, requiring no oil pipe. The camshaft skew gear and oil pump gear are lubricated by oil sprayed from the oil hole drilled in the oil pump case.The engine oil fed under pressure by the oil pump is delivered to the oil cooler. <DR>The oil pump, of the trochoid type, is driven by the skew gear mounted on the camshaft.An oil strainer is mounted at the suction port of the oil pump and the engine oil drawn up by the oil pump is fed under pressure to the oil filter. On models with oil cooler, the engine oil is fed under pressure to the oil cooler. Through the oil hole in the oil pump case and notch in the oil pump shaft, the engine oil in the oil main gallery is splashed to lubricat the oil pump gear. The oil strainer of 6DR5 engines has a relief valve that prevents overloading of the oil cooler or oil filter due to high oil pressure caused during high engine speed or low oil temperature.In the trochoid pump, when the inner rotor turns, the outer rotor also turns with it in the same direction; however, the different number of lobes and difference in center position between the inner and outer rotors vary the spaces formed between them to provide pumping action. (2) Oil Cooler The oil cooler is an equipment for heat exchange between the coolant and oil fed under pressure from the crankcase water jacket and oil pump, respectively.The oil cooler has a bypass valve that opens when the element passes less oil as it becomes clogged. (3) Oil Filter <D3>The oil filter is a type incorporating both the full-flow and bypass filters. The element is a spin-on type that allows easy replacement.The engine oil filtered through the full-flow filter is delivered to the crankcase oil main gallery and the oil circulating through the bypass filter returns through the crankcase to the oil pan. The oil pump cover has a relief valve that reroutes the engine oil to the oil pan when the oil pressure exceeds a predetermined level, thus preventing the lubricating system from being overloaded.<DR>(a) Spin-on type The oil filter is a full-flow type using filter paper. On the oil filter head, the regulator valve is mounted. Element is a spin-on type that allows easy replacement.The full-flow filter includes a bypass valve that opens when the difference in pressure between the filtered and unfiltered oil exceeds a set level as a result of clogged element, thus allowing the unfiltered oil to flow into the engine.The oil filter head has a regulator valve that allows engine oil to escape to the oil pan when oil pressure exceeds the specified level, thus preventing overloading of the lubrication system.(b) Center bolt type The oil filter is a full-flow type using filter paper. On the oil filter head, the regulator valve and oil bypass alarm are mounted.The oil filter head has a regulator valve that allows engine oil to escape to the oil pan when oil pressure exceeds the specified level, thus preventing overloading of the lubrication system.The oil bypass alarm system causes the valve to open automatically when the oil pressure difference before and after filtration exceeds specified level, allowing unfiltered engine oil to flow to the engine inside. The oil bypass alarm has an electrical contact that closes to illuminate a pilot lamp, warning element loading to the driver when the valve is opened.(4) Lubrication of Parts The engine oil routed from the oil filter to crankcase oil main gallery lubricates all engine parts as detailed below before returning to the oil pan.(a) Main bearing and connecting rod bearing There is an oil passage provided from the oil main gallery to each main bearing. The oil flows through the oil hole to lubricate the main bearing and passes through the oil passage drilled into the crankshaft to lubricate the connecting rod bearings. On D3, the oil then passes through the oil hole in the connecting rod to lubricate the connecting rod small-end bushing, while spraying from the oil jet to cool down the piston.On DR, no oil holes are drilled in the connecting rod.(b) Camshaft Camshaft bushings are lubricated by the oil flowing through the oil passages leading from the oil main gallery to each bushing.There is an oil hole provided in the journal at the front end of engine that serves as an oil passage to lubricate the camshaft gear and valve mechanism.(c) Valve mechanism The engine oil that has lubricated No. 1 camshaft bushing passes through the oil hole and pipe provided at the top portion of crankcase to the cylinder head.The engine oil then goes through the front-end rocker shaft bracket into the rocker shaft, lubricating each rocker bushing. At the same time, it sprays from the oil hole at top of rocker to lubricate the surfaces over which the valve cap slides and valve stem. The oil then passes through the push rod holes in the cylinder head and crankcase to lubricate the tappets and camshaft cams before returning to the oil pan. (d) Timing gear The timing gear idler gear bushing is lubricated by the engine oil routed from the oil main gallery, part of which spraying from the idler gear oil hole to lubricate each gear.The camshaft gear and thrust plate are lubricated by the engine oil routed from No.1 camshaft bushing through the camshaft oil hole. On 4D31 and 4D31-T the idler shaft is provided with an oil pipe for the forced-lubrication of the auto timer.