1995 Mariner Mercury Outboards Service Manual 50HP 4-Stroke, Page 128Get this manual
Valves 1Clean the carbon deposits from the valveDiscard any cracked, warped, or burned valves Measure the valve stem to check for wearReplace valves if not in specification
Valve Springs
Check free length limit of each springReplace valve springs if not in specificationValve Stem Diameter
Valve Spring Free Length Limit
1.5691.491 in(39.8537.85 mm)
Intake Valve Exhaust Valve 3
0.21560.2161 in(5.4755.490 mm) 0.21500.2156 in(5.4605.475 mm)
Check the valve face for pittingValves faces that are pitted must be refaced
Check each spring on flat surface using squareRotate spring and check space between the top coil and squareReplace valve springs if not in specification