1972 Johnson 4HP Outboard Motor Service Manual, Page 37Get this manual
Sinee the pistons, with the piston rings, reeeive the foree of eombustion in the eylinder head, it is 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 perfeetly round and the piston rings eorreetly seated in their groovesCONNECTING RODS, CRANKSHAFT, AND BEARINGS The eonneeting rods provide linkage between the piston and erankshaftThe foree of eombustion, applied reeiproeating straight thrust, to the piston in is eonverted to rotating power at the erankshaft through the linkage of the eonneeting rodThe erankshaft is of the two-throw type and is supported three east-in main bearingsCOOLING SYSTEM power head is water eooledwater driven the driveshaft, forees water through ehannels in the power headHeated water is discharged through the exhaust tubeThe 4
REMOVAL OF POWER HEAD
Remove earburetor, leaf valve assembly, and manifold as deseribed in Seetion 3Remove flywheel, spark plugs, and magneto as deseribed in Seetion 4