1978 Evinrude Outboards 9.9/15HP Service Manual, Page 54Get this manual
DESCRIPTION The power head consists of the cylinders, pistons, rods, crankshaft, and crankcaseThe power head has two horizontally mOWlted cylindersAlternate firing order is used so that each cylinder delivers one power impulse per crankshaft revolutionSee Figure 5-1 for two stroke theory
AFUEL INTAKE AND EXHAUST
EXHAUST PORT