Chrysler 6, 7.5, 180 Sailor Outboard Motors Service Manual, OB 3330, Page 90Get this manual
_ POWERHEAD GENERAL
An engine needs three basics to run: proper fuelair mixture, compression, and spark at the right timeThe information in this section is concerned with compression, or the parts of the power head that go into the development of compression compressed mixture The resulting explosion forces the piston down which in turn rotates the crankshaftFigure 1AAs the piston moves downit first uncovers the exhaust port The exhaust escapes through this port and the combustion chamber pressure falls Meanwhile, fresh supply of air fuel mixture is being compressed in the crankcase by the do wn stroke of the piston Figure 1BAs the piston nea rs the bottom of this stroke, it uncovers the inl et ports and this fresh air fuel mixture rushes into the combustion chamber in an effort to equalize the pressure between the crankcase and combustion chamberThe flow pattern of the fresh air fu el mixture pushes the burned exhaust fuel from the cylinder Figure 1CNow the compression stroke beginsthe intake po rts and exhaust ports are covered by he ri sing piston As pressure increases in the combustion chamber, it decreases in the crankcase his decrease in pressure permits new air fuel mi xt ure from the carburetor to enter through the reed valvethus preparing the next cylinder charge Figure DThe recirculating passages built into the cylinder block are designed to transfer any unburned fue in one cylinder to the intake area of the other cyl inderFigure 2In th mannerall fuel is consumed in th combustion chamber rather than being allowed to vent overboard into the lake or waterway