Spark Plug Inspection And Replacement - Mercury 250 XS OptiMax Operation, Maintenance & Installation Manual

This model has three corrosion control anodes on the gearcase—two above
and one below the anti‑ventilation plate. A fourth anode is located on the
bottom of the clamp/swivel bracket assembly.
All anodes require periodic inspection, especially in saltwater (refer to the
Inspection and Maintenance Schedule). Replace any anodes before they are
50% corroded. Never paint or apply protective coating on an anode, as
effectiveness of the anode will be reduced.

Spark Plug Inspection and Replacement

Damaged spark plug boots may emit sparks that can ignite fuel vapors under
the engine cowl, resulting in serious injury or death from a fire or explosion.
To avoid damaging the spark plug boots, do not use any sharp object or
metal tool to remove the spark plug boots.
1. Remove the spark plug leads by twisting the rubber boots while pulling
them off the spark plugs.
2. Remove the spark plugs. Replace the spark plug if the electrode is worn;
the insulator is rough, cracked, broken, or blistered; or if the precious
metal is not visible on the spark plug electrode.
MAINTENANCE
WARNING
!
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a - Corrosion control
anodes (three on
gearcase)
b - Corrosion control anode
(one on clamp/swivel
bracket)
eng