5008471 EVINRUDE TILLER KIT

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(1) Crankcase one
(2) Crankcase two
(3) Oil panThe engine utilizes a split crankcase to produce greater durability and operate more quietly. The crankcase is split into two parts, crankcase one, which houses the parts for combustion and crankcase two, which complete crankcase one and produces low-noise.The engine uses a hanger type of crankshaft support which allows for easy disassembly and the lining of the cylinder is a linerless type. This configuration offers good cooling performance and excellent resistance to wear as is little affected by distortion.Cylinder Head
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(4) Intake port
(5) Exhaust portThe cylinder head is made of an alloy of iron and copper or chromium for greater strength and durability. The intake and exhaust passages are cast into the cylinder head.The cylinder head of four valves, is provided with double intake passage to ensure appropriate air suction and give an optimum swirl.The cross-flow type intake/exhaust passages in these engines have openings at both sides of the cylinder head. The suction air can be protected from being heated and expanded by exhaust gas. The cool, high-density suction air has high volume efficiency and raises the power of the engine. Furthermore, distortion of the cylinder head by exhaust gas is reduced because intake passages are arranged alternately.Piston
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(6) Molybdenum Disulfide coatingThe reciprocating motion of a piston in the engine cylinder creates the forces for the suction, compression, power, and exhaust cycles.To be strong yet light, pistons are constructed of cast iron or aluminum alloys. Reinforcing ribs are used to keep the piston as light as possible.The piston head shape depends on the combustion chamber. A relatively deep concave head is used for direct injection engines, whereas a flat or slightly concave one is used for engines with pre-combustion chambers.The ring grooves are cut around the piston to fit the piston rings. The grooves are shaped to the proper rings for good control of oil and blow-by. The lower groove in which the oil ring is inserted has many holes for oil collected by oil ring to flow back to the crankcase.The piston lands are the areas between the ring grooves which hold and support the piston rings in the grooves. A fine groove called a “heat dam” is provided on the top land to protect the top ring from high temperatures.The skirt of the piston is the outside part below the ring grooves. The piston is kept in alignment by the skirt. The piston skirt has a layer of molybdenum disulfide, which decreases the piston slap noise and prevents scorching.The molybdenum disulfide is a solid lubricant, like Graphite or Teflon. This material helps not to wear the metal even with little lube oil.Piston Rings
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(7) Top compression ring
(8) Intermediate compression ring
(9) Oil control ringPiston rings are classified as compression and oil control rings. This engine has two compression rings around the piston head and one oil ring just below the top two rings.The compression rings prevent gases from leaking by the piston during the compression and expansion strokes. The compression rings seal by expanding out against the cylinder wall. The rings expand by tension and also by combustion pressure behind the rings during the expansion stroke. The compression rings are split for easy assembly on the piston.The top compression ring is a keystone type ring to get durability against heavy load.The intermediate compression ring is an undercut ring to prevent shortage of oil.The main job of the oil control ring is to wipe the excess oil from the cylinder walls. This oil is fed through slots in the rings to holes in the piston groove, where the oil returns to the crankcase. For better oil control, spring expanders are often used under the oil control ring.The piston rings are made of hardened cast iron. To reduce the wear on the ring, the rings are plated with chrome on the contact faces, or are coated the contact faces with molybdenum disulfide.Connecting Rod
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(10) Small end bushing
(11) Connecting rod
(12) Crankpin bearingThe connecting rod must be light and yet strong enough to transmit the thrust of the piston to crankshaft.The large end of connecting rod has a crankpin bearing (split type) and the small end has a small end bushing (solid type).Crankshaft
Illustration 6 g02918817The crankshaft converts the up-and-down motion of the pistons into rotary motion. The crankshaft ties together the reactions of all the pistons into one rotary force that drives the machine.The crankshaft is made of tough special alloy steel. The journals, pins, and oil seal sliding portions are induction hardened to increase the hardness for higher wear resistance.All the journals are supported by split type bearings. The thrust bearings are shown in the Illustration.The crankshaft is provided with an oil gallery, through which engine oil is fed to the crankpin portion, and lubricates the crankshaft.Camshaft
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(13) Camshaft gear
(14) Camshaft stopper
(15) CamshaftThe camshaft is normally driven by gearing from the crankshaft.The camshaft is made of special cast iron, and the journal and cam sections are chilled to resist wear. One intake and one exhaust cam is provided for each cylinder.The journal diameters are large to permit removal of the shaft from the camshaft bore. The journal sections are force-lubricated.