1978 Johnson 55 HP Outboards Service Manual, Page 28Get this manual
CORE PLUGS If necessary, remove core plug to clean out slow
speed orifice holes, Figure 3-1If leakage occurs at core plug area, follow these steps:
aIf leakage is slight, smart tap with hammer and flat end punch in the center of the core plug will normally correct this conditionSee Figure 3-16bIf leakage persists, drill 18 inch (3.2 mm) hole through the center of the core plug to depth of not more than 116 inch (2 mm) below its surfaceWith punch carefully pry out the core plugSee Figure 3-17cInspect and clean casting contact area; if nicks, scratches, or an out-of-round condition exist, the casting will have to be replacedIf the casting opening is normal, apply bead of OMC Adhesive to the top edge of new core plug and place the new core in the casting opening, convex side upFlatten to tight fit with flat end punch and hammerCheck for leakageLEAF VALVES aInspect the leaf plate assembly and disassemble The leaf valves must be free from all varnish and gum, and the leaves must be perfectly flat and without distortion so that they form seal with the leaf plate baseSee Figure 3-18if necessary