1978 Johnson 4HP outboards Service Manual, Page 62Get this manual
Before installing new piston rings, check gap between ends of ring by placing ring in its respective cylinder bore, then pushing ring down in the bore slightly with the bottom of the piston to square it upSee Figure 5-15 Check for ring groove clearance with feeler gageSee Figure 5-16Correct gap and groove clearances are given in Section 2 fectly good cylinder walls, pistons, and rings can be ruined in few minutes of operation unless all forms of grit are removed before assemblyWork in clean surroundings and with reasonably clean handsCoat all bearing surfaces, cylinder walls, etc with clean oil before assemblyWhen the use of "oil" is specified, we recommend OMC outboard lubricant
Always use new gaskets throughout when reassembling the powerheadApply OMC Gasket Sealing Compound lightly to both sides of cylinder head gasket and to outer diameter of crankshaft sealDo not use sealer if so stated on the gasketPISTONS, WRIST PINS, AND CONNECTING RODS aThe relative positions of pistons and connecting rods must be considered in reassemblyPistons must be installed as illustrated in Figure 5-178 036