Yanmar 1GM User Manual page 137

MULTICYLINDER ENGINES
131
Cylinder block
Core plug Installation tool
Sealing edge
before Installation
Strike here
W l t h h 7
Removal and Installation
Remove plug
Core Plug Replacement
Check the condition ofall core plugs in the block when-
ever the engine is out of the boat for service. If any signs
of leakage or corrosion are found around one core plug,
replace them all. Core plugs in the cylinder block prevent
damage to the block should the coolant freeze. The cylin-
der block of 2GM, 3GM and 3HM engines is equipped
with cast iron, removable cylinder liners. See Cylinder
Liners in this chapter.
NOTE
A machine shop can replace core plugs in-
expensively.
If
machine work on the engine
is necessary, have the core plugs replaced at
the same time.
CAUTION
Do not drive core plugs into the engine cast-
ing. It will be impossible to retrieve them
and they can restrict coolant circulation, re-
sulting in serious engine damage.
1. Tap the bottom edge of the core plug with a hammer
and drift. Use several sharp blows to push the bottom of
the plug inward, tilting the top out (Figure 81).
2. Grip the top ofthe plug firmly with pliers. Pull the plug
from its bore (Figure 82) and discard.
NOTE
It is also possible to remove core plugs by
drilling a hole in the center ofthe plug and
prying it out with an appropriate size drift
or pin punch. When removing a large core
plug, the use of a universal impact slide
hammer is recommended.
3. Clean the plug bore thoroughly to remove all traces of
the old sealer. Inspect the bore for any damage that might
interfere with proper sealing of the new plug.
4. Coat the inside diameter ofthe plug bore and the outer
diameter of the new plug with sealer. Use an oil-resistant
sealer ifthe plug is to be installed in an oil gallery or a wa-
ter-resistant sealer for plugs installed in the water jacket.
5. Install the new core plug with an appropriate size core
plug installation tool (Figure 83), driver or socket. Posi-
tion the outside edge of the plug 2-3 mm (0.08-0.12 in.)
inside the block.
6. Repeat Steps 1-5 to replace each remaining core plug.