1971 Johnson 4HP Outboard Motors Service Manual, Page 37Get this manual
Sinee the pistons, with the piston rings, foree of eombustion in the eylinder head, 1t lS neeessary that both the pistons and piston rings properly fitted to form seal between the piston head and eylinder wallsretain power within the eylinder head, the eylinder must feetly round and the piston rings eorreetly seated in their groovesRODS, AND BEARINGS
REMOVAL OF POWER HEAD
Remove earburetor, leaf valve assembly, and manifold as deseribed in Section 3Remove flywheel, spark plugs, and magneto as described in Seetion 4If starter does not require serviee, leave it attaehed to the erankcaseIf removal for serviee is necessary, see Seetion 7
The eonnecting 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 connecting rodThe crankshaft is of the two-throw type and is supported three east-in main bearingsCOOLING SYSTEM power head is water cooledwater driven the driveshaft, forces water through channels in the power headwater is discharged through the exhaust tubeThe 4