Mercury 15 EFI FourStroke, Service Manual

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Valve Stem Outside Diameter
Intake
5.46–5.48 mm (0.215–0.216 in.)
Exhaust 5.44–5.46 mm (0.214–0.215 in.)
3. Measure the margin thickness of the valve. Replace the valve if out of specification.
20972
Valve
Margin thickness
Intake 0.55 mm (0.0217 in.)
Exhaust 1.00 mm (0.0394 in.)
Valve Springs
1. Check the free length of each valve spring. Replace the valve springs if they are out of specification.
20973
Valve Spring
Free length
31.50–32.85 mm (1.240–1.293 in.)
2. Measure the valve spring tilt. Replace the valve springs if they are out of specification.
NOTE: Check each spring on a flat surface using a square. Rotate the spring and check the space between the top coil
and the square.
20974
Valve Spring
Tilt limit
1.1 mm (0.043 in.) maximum
Cylinder Head Resurfacing
NOTE: The following procedure should only be attempted for minor scratches and minor warpage. Severe scratches or severe
warpage cannot be corrected with resurfacing the head.
1. Place a sheet of 400–600 grit wet sandpaper on a flat surface.
2. Apply a light downward pressure on the head. Move the head in the pattern shown.
3. Rotate the head several times during the resurfacing procedure to avoid removing material from one side.
Cylinder Head
Page 4B-16 © 2018 Mercury Marine 90-8M0125265 eng NOVEMBER 2017