Mercury Optimax Models 135, 150, Direct Fuel Injection., Page 251Get this manual
POWERHEAD
CLEANING PISTON RING GROOVES
Keystone (tapered) ring grooves
CAUTION
Care must be taken not to scratch the side surfaces of the ring grooveScratching the side surface of the ring groove will damage the ring groove1Use bristle brush and carbon remover solution to remove carbon from side surfaces2A tool can be made for cleaning the inner diameter of the tapered ring groovesThe tool can be made from broken tapered piston ring with the side taper removed to enable the inside edge of the ring to reach the inner diameter of the grooveCarefully scrape carbon from inner diameter of ring groovesCare must be taken not to damage the grooves by scratching the side surfaces of the groovesPiston with two half keystone (half tapered) rings (135150 Models)