1977 Evinrude 4HP Outboards Service Manual, PN 5303, Page 46Get this manual
Since the pistons, with the piston rings, receive the force of combustion in the cylinder head, it is necessary that both the pistons and piston rings be properly fitted to form seal between the piston head and cylinder wallsTo retain maximum power within the cylinder head, the cylinder must be perfectly round and the piston rings correctly seated in their groovesCONNECTING RODS, CRANKSHAFT, AND BEARINGS The connecting rods provide linkage between the piston and crankshaftThe force of combustion, applied to the piston in reciprocating straight line thrust, is converted to rotating power at the crankshaft through the linkage of the cormecting rodThe crankshaft is of the two-throw type and is supported by two cast-in main bearings and an upper needle bearingCOOLING SYSTEM The HP power head is water cooledA water pump, driven by the driveshaft, forces water through channels in the power headHeated water is discharged through the exhaust tube REMOVAL OF POWER HEAD
aRemove carburetor, leaf valve assembly, and manifold as described in Section 3bDisconnect cable connectorsRemove spark plugs, ignition coils and flywheelRemove sensor, charge coil and plate assembly as described in Section 4cIf starter does not require service, leave it attached to the crankcaseIf removal for service is necessary, see Section 7