FALL 2014 | MARINE TECHNICIAN TODAY
23
Marine Electronic
Fuel Injection
and
Performance Boater
M
ost marine technicians familiar
with sterndrive EFI can trace
its introduction into the
marketplace to the early 1990s. There were
offerings based on General Motors and Ford
engines. 1993 is often the recognized year
of the introduction, but it was not. It was
really many years earlier. The forgotten fuel
injection engine was offered by MerCruiser
from 1987 through 1989, six years earlier!
It was called the 320 EFI. It used a General
Motors 350 CID block and a totally GM designed EFI system. In fact, the
system was very similar to the tuned port injection used on GM’s Firebird
and Camaro in the 1980s.The EFI system was ahead of its time for the
marine industry, and there was no consumer demand yet, so MerCruiser
dropped it from its model lineup mid-year 1989.
Because of the re-introduction of EFI, 1993 was a new era for the marine
industry. With help fromGM’s Powertrain & Delphi, MerCruiser introduced
an EFI system that used an ECM (Electronic Control Module) called MEFI-
1(Marine Electronic Fuel Injection). To compete with MerCruiser, OMC
introduced a system with the help of Ford on a 5.8 liter engine using Ford’s
EEC (Electronic Engine Control) EFI module.
Since MerCruiser was a much larger supplier of sterndrive power
packages than OMC, the GM designed system was the most prominent
in the industry. Also GM heavily marketed the new computer controller
(ECM) for the marine industry. The improvements promoted were turn-
key starting, improved emissions, maximized spark advance due to sensor
inputs, reduced spark knock, keeping the stoichiometric ratio correct for
altitude changes, over-speed protection, reduced RPM if a critical problem
is identified by the engines computer, self-diagnostic capabilities, and data
output for aiding a technician in troubleshooting engine running problems.
As technology progressed, GM introduced MEFI-2, MEFI-3 and MEFI-4
ECMs. As the versions changed, the processors got more powerful, fuel
mapping was improved, and more fault codes could be stored to aid the
technician in troubleshooting problems. The MEFI-4 ECM supersedes all
the older versions, and if you have a failure of an older ECM, it must be
updated to the new version. A wiring harness kit comes with the new ECM
to adapt the old wiring harness to the new ECM.
The MEFI ECM system is referred to as a speed-density system. The
ECM receives information from sensors that measure engine speed and
air density. The engine speed information is supplied from the ignition
systems distributor and the air density information is supplied from the
MAP (manifold absolute pressure) sensor. The distributor tells the ECM
what the engine speed is and controls sparkmanagement. TheMAP sensor
tells the ECM about the air flow through the intake manifold and assists in
determining engine load. When throttle is advanced, vacuum drops in the
intake manifold and the air pressure density in the intake manifold rises.
THE
PERFORMANCE
CORNER
By JohnMosetti
.
OMC Cobra 5.8 Ford marine
fuel injection engine
.
FAST Self leaning EFI system
