1995 Mariner Mercury Outboards Service Manual 50HP 4-Stroke, Page 109Get this manual
6 Turn the driven gear and align the "1" mark with the the cylinder head mark "t:"
Timing Belt Installation
Timing Belt Installation Notes: Protect the timing belt from water and oilUse care not to scratch the beltDo not use any metal device to help stretch the belt onto the driven gearAlign drive gear mark with cylinder mark30033