1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 266Get this manual
8Install O-ring [2.739I (69.57mm) I.DIt is recommended O-ring be installed even if pump did not originally have O-ringInsert pump and motor assembly into Power Trim housing, with rocker arm positioned as shown Brush Replacement ("Square" Motor)
1Brush replacement is recommended if brushes are pitted, chipped, or if distance (a) between the brush pigtail and end of brush holder slot is 116I or lessCheck the distance with armature installed, as shown18453
aO-ringRocker Arm