Mercury MERCRUISER, Service Manual, Page: 310 / 566

Wire Color Code Abbreviations
Wire Color Abbreviations
BLK Black BLU Blue
BRN Brown GRY Gray
GRN Green ORN or ORG Orange
PNK Pink PPL or PUR Purple
RED Red TAN Tan
WHT White YEL Yellow
LT or LIT Light DK or DRK Dark
Spark Plug Removal, Inspection, and Installation
NOTE: Refer to the specifications presented earlier in this section for spark plug part numbers and gap information.
Removal
1. Disconnect the spark plug wires from the spark plugs.
NOTE: Use care when removing the spark plug wires from the spark plugs. Twist the boot 1/2 turn before removing. Firmly
grasp and pull on the boot, not the wire.
2. Remove the spark plugs.
NOTE: A thin‑walled spark plug socket may be required.
Inspection
1. Examine each spark plug. All plugs must be from the same manufacturer and have the same spark plug number.
2. Inspect each plug for worn electrodes and for glazed, broken, or blistered porcelain. Check the joint between the insulator
and the shell for cracks. Replace as necessary.
Installation
1. Clean the cylinder head spark plug seat.
2. Adjust the spark plug gap with the appropriately sized, round‑tipped feeler gauge.
IMPORTANT: In the absence of a torque wrench or if limited access prevents the use of a torque wrench, hand‑tighten the
spark plugs until they seat in the cylinder head and then securely tighten with the appropriate ratchet and socket.
3. Install the spark plugs and tighten them to the specified torque.
Description Nm lb‑in. lb‑ft
Spark plugs (new cylinder head) 30 – 22.1
Spark plugs (used cylinder head) 14 123.9 –
4. Install the spark plug wires in the proper order. Refer to
Spark Plug Wires
for details.
Spark Plug Wires
Inspection
NOTE: Use care when removing the spark plug wires and the boots from the spark plugs. Twist the boot 1/2 turn before
removing. Firmly grasp and pull on the boot to remove the wire.
1. Inspect the spark plug wires, the plug wire boots, and the coil wire for damage.
2. Check the spark plug wires and the coil wire for continuity using a multimeter.
IMPORTANT: The spark plug wires must have the correct resistance to prevent radio frequency interference (RFI) and still
deliver full spark. Nonresistor spark plug wires are not acceptable. The resistance for each 30 cm (1 ft) of wire length must
not be more than 8,000 ohms and not less than 2,000 ohms. Replace any wires that are not as specified.
3. Replace any damaged wires.
4. Check for correct routing. Keep the spark plug wires as far away as possible from the engine wiring harness.
Installation
IMPORTANT: Use only Mercury marine‑grade spark plug wires. Use of aftermarket spark plug wires may result in performance
issues not covered by the Mercury limited warranty.
NOTE: Replace one spark plug wire at a time to reduce the risk of a routing error.
1. Disconnect each spark plug wire as it is to be replaced.
Waste Spark System
Page 4B-4 © 2016 Mercury Marine 90-8M0099748 eng DECEMBER 2015