1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 196Get this manual
Replacement of Upper Main Bearing Seal65 The presence of oil under the flywheel indicates leaking upper main bearing sealTo replace the seal, the bearing must be removed from the crankshaftFollow the portions of the powerhead removal, disassembly, reassembly and installation necessary to replace the upper main bearing seal
Disassembly of Powerhead65
Discard all gaskets from the powerhead componentsScrape or peel off the gasket, being careful not to remove any metal with the scraper1Remove the eighteen intake manifold screwsRemove the intake manifold from the crankcase2Remove the five thermostat cover screwsTap the cover around its edge with soft mallet to break the sealCarefully separate the cover from the cylinder head and remove the two pressure relief valve springs34Remove the two pressure relief valves