Mercury 25 EFI FourStroke User Manual page 114

Each anode requires periodic inspection, especially in saltwater
which will accelerate the erosion. To maintain this corrosion
protection, always replace the anode before it is completely
eroded. Never paint or apply a protective coating on the anode
as this will reduce effectiveness of the anode.
One anode is installed in the engine block. Remove anode at
location shown. Install anode to cover with bolt. Tighten bolt to
specified torque. Reinstall cover with new gasket. Tighten bolts
to specified torque.
a - Cover
b - Anode
Description
Anode bolt
Cover bolt (2)
MAINTENANCE
Nm
104
b
a
10230
lb. in.
6 53
6 53
lb. ft.
eng