Mercury MERCRUISER, Service Manual, Page: 309 / 566

DMT 2004 Digital Multimeter 91‑892647A01
A C O M m A V H z
mV
V
H z TEMP
m A
A
IG
IP OFF
H z
TEMP
4516
Measures RPM on spark ignition (SI) engines, ohms, amperes, AC and DC
voltages; records maximums and minimums simultaneously, and accurately
reads in high RFI environments.
Waste Spark System Specifications
Waste spark system is an ignition system used with some two‑ and four‑stroke cycle internal combustion engines. In a wasted
spark system, the spark plugs fire in pairs even though one is on its compression stroke and one is on its exhaust stroke. The
extra spark on the exhaust stroke has no effect and is thus "wasted." This design has the number of components in a typical
ignition system, while the extra spark, against much reduced dielectric resistance, barely impacts on the lifespan of modern
ignition components. In a typical engine, it requires only about 2–3 kV to fire the cylinder on the exhaust strokes. The remaining
coil energy is available to fire the spark plug under compression (typically about 8–12 kV). PCM 112 ignition system uses
double‑ended driverless ignition coils. Each coil is a double‑ended waste spark, so one coil will fire two cylinders. One cylinder
will be on the compression stroke and the other cylinder will be on the exhaust stroke.
Coil
Description Specification
Primary coil resistance 0.30–0.50 Ω
Secondary coil resistance 7,200–8,800 Ω
Spark Plugs
Engine OEM Spark Plug Gap
6.2L NGK BPR5EFS‑13 1.30 mm (0.051 in.)
Firing Order and Ignition Timing
Description Specification
Firing order 1‑8‑4‑3‑6‑5‑7‑2
Ignition timing PCM
Ignition Components
a - Battery
b - PCM
c - Ignition coils
d - Spark plugs
e - Crankshaft position sensor
For diagnostics also refer to the
PCM 112 Diagnostic Manual
.
b
c
a
e
d
59408
Waste Spark System
90-8M0099748 eng DECEMBER 2015 © 2016 Mercury Marine Page 4B-3