1968 Evinrude Speedifour, Starflite 85HP Service Manual, Page 39Get this manual
DESCRIPTION The power head consists of the cylinders, pistons, connecting rods, crankshaft, and crankcaseThe power head has two banks of horizontal1y-mounted cylinders in "V" formation 90 apart The firing order is combined so that each cylinder delivers one power impulse crankshaft revolutionthus giving one power impulse at every 90 degrees of crankshaft rotationSee Figure 5-1CRANKCASE AND CYLINDERS provide equal fuel vapor distribution to the four cylinders, the crankcase is divided into four equal areas, and each is sealed off from the others through the use of compression type sealing rings the crankshaft websfour crankcase distribution chambers must isolated from each other at times to prevent compression leakage between cylindersSee Figure 5-1CYLINDER HEADS There separate cylinder heads for each bank of cylindersThe cylinder head covers numbered to correspond to the ignition firing orderThe starboard cylinder head cover is numbered and lower and the port cylinder head cover is numbered and lowerPISTONS The pistons, with the piston rings, receive the force of combustion in the cylinder head, so it is necessary that both the pistons and piston rings properly fitted to form seal between the piston head and cylinder wallsretain maximum power within the cylinder above the piston head, the cylinder must perfectly round and the piston rings correctly seated in their groovesFUEL and EXHAUST CYLINDER NO1 XHAUST MANIFOLD