Inspection - Mercury MerCruiser Service Manual

Engine Inspection and Assembly
2. Install the cylinder head core hole expansion plug. Core plug should be recessed 0.158 cm (0.062 in.) with the inside
chamfer of the cylinder head core hole on the aft end of cylinder head.
a
Tube Ref No.
Loctite 242 Threadlocker
66
3. Repeat procedure on opposite head.
NOTE: Each head needs a core plug installed in the aft end of the cylinder head.

Inspection

Cylinder Head
1. Inspect the sealing surfaces for burrs, scratches, deep nicks, erosion, or other damage.
2. Inspect for cracks in exhaust ports, water jackets, and combustion chambers (especially around spark plug holes and valve
seats).
3. Replace the cylinder heads if necessary.
4. Inspect for rusted, damaged, or leaking core plugs. Replace core plugs if necessary.
5. Inspect for corrosion around cooling passages.
6. Check the flatness of cylinder head gasket surfaces—head, exhaust, and intake gaskets, using a machinist's straightedge
and feeler gauge. Take measurements diagonally across the cylinder head from all four corners and lengthwise straight
down the center of the cylinder head.
b
a
Page 3B-44
Description
c
30171
© 2016 Mercury Marine
57310
Where Used
Outside diameter of core expansion plug
Head deck shown, exhaust and intake decks are similar
a - Cylinder head deck
b - Machinist's straightedge
c - Feeler gauge
90-8M0099748 eng DECEMBER 2015
Core expansion plug installed in aft end
of head
a - Core expansion plug
Part No.
92-809821