Mercury 200 Sport-Jet Operation & Maintenance Manual page 63

IMPORTANT: The color of the plug may not accurately reflect its condition. To
accurately diagnose a faulty plug, inspect the precious metal on the plug's
electrode. If no precious metal is visible, replace the plug.
a - Precious metal
5. Set the spark plug gap. Refer to General Information ‑ Specifications.
• Ensure that all of the spark plugs are properly gapped prior to
installation.
• Measure the gap with a feeler gauge or pin gauge. Never use a
wedge‑type gap checking tool to inspect or to adjust the gap.
• If an adjustment is necessary, do not pry or apply any force on the
center electrode. This is critical with any type of spark plug that has a
wear surface, such as platinum or iridium added to either the ground
electrode or the center electrode.
• When it is necessary to widen the gap, use a tool that only pulls back
on the ground electrode without touching the center electrode, the
porcelain, or the wear portion of the ground electrode.
• When it is necessary to close the gap, gently tap the plug ground
electrode on a hard surface.
6. Before installing spark plugs, clean off any dirt on the spark plug seats.
Install the plugs finger‑tight and then tighten an additional 1/4 turn or
tighten to the specified torque.
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