1979 Johnson 2HP Outboards Service Manual, Page 39Get this manual
5-6 ring landsSee Figure 5-13Check piston for size and roundness, using micrometerCorrect sizes given in Section 2Before installing new piston rings, check gap between ends of ring placing ring in cy1inder then pushing ring down in the s1ightly See Figure 5-14Check with the bottom of the piston to square it for ring groove clearance with feeler gageSee Figure 5-15Correct gap and groove clearances given in Section 2 REASSEMBLY OF POWER HEAD
Proceed slowlyMake forced assemblies unless press fits called for, and make "dry" assembliessure parts to assemblecl clean and free from dirt and gritperfectly good cylinder wall, piston, and rings ruined in few minutes of operation unless forms of grit removed before assemblyWork in clean surroundings and with reasonably clean handsCoat bearing surfaces, cylinder wall, etc with clean oil before assemblyWhere the use of is specified, we recommend Outboard Lubricant
Figure 5-13Cleaning Piston Ring Groove
Always use new gaskets coated lightly with gasket sealing compound part number 317201 when reassembling the power headPISTON, WRIST AND ROD