1984-1986 Mercury Force 4HP Outboards Service Manual, Page 37Get this manual
SECTION
POWER HEAD
GENERAL
An engine needs three basics to run: proper fuelair mixture, compression and spark at the right limeThe information in this section is concerned with compression, or the parts 01 the powerhead thai go into the development of compression
tinuing to build pressureThe fresh fuel moves from the crankcase (high pressure area) thru the intake ports to the combustion area (low pressure area)Refer to Figure -A
COMPRESSION
The piston now has reached its towest paint of travel (bottom dead center, B.D .C) and starts to move upward in the cylinder As it moves towards its highest point of travel (top dead center.D.C it covers the ports and compresses the fresh fuel charge for combustionFigure 1-B
DESCRIPTION