1970 Johnson 1.5 HP Outboard Motor Service Manual, Page 36Get this manual
5-6 ring landsSee Figure 5-13Check piston for size and using micrometerCorrect sizes given in Section 2Before installing new piston rings, check gap between ends of ring placing ring in cylinder then pushing ring down in the slightly with the bottom of the piston to square it See Figure 5-14Check 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 assembled clean and free from dirt and gritperfectly good cylinder wall, piston, and rings can ruined in few minutes of forms of grit removed before assemblyWork in clean ings and with reasonably clean handsCoat bearing surfaces, der wall, etc with clean before assemblyNOTE Always use new gaskets throughout when reassembling the power headPISTON, WRIST PIN, AND ROD
Figure 5-13Cleaning Piston Ring Groove