1971 Johnson 40HP outboards Service Manual, Page 40Get this manual
DESCRIPTION The power head consists of the cylinders, pistons, rods, crankshaft, and crankcaseThe power head has two horizontally mounted cylindersAlternate firing order is used so that each cylinder delivers one power impulse per crankshaft revolutionSee Figures 5-1 and 5-2
EXHAUST PORT EXHAUST GASES