1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 68Get this manual
Engine Synchronization and Adjustment100 and 155 Set Timing Pointer INotel Remove both remote control cables from the eng ine before perform ing the following synchronizations and ad justmentsINotelf the timing pointer or intake manifold has been disturbed, check the top dead center timing pointer alignment1'" To prevent accidental starting of the motor, disconnect the spark plug leads and remove the spark plugs2Install OMC Special Tool PIN 384887 (Piston Stop) No.1 spark plug hole