FALL 2014 | MARINE TECHNICIAN TODAY
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by completing a series of dynamometer tests as mentioned above. One
example of this is when I worked on a boat where the boat owner changed
his exhaust system to a full header style exhaust and also changed the
camshaft to one of more lift and duration. The engine ran so poorly that
he actually lost horsepower and torque. The main reason that the engine
ran so poorly was the camshaft change; it directly affected the vacuum
characteristics of the engine and the MAP signal was now incorrect. The
ECM could not compensate for the difference in the MAP signal because it
was operating outside of the mapping parameters of the stock ECM tune.
So keep in mind, once again, currently all marine OEM stock computer
control engines have no manual adjustments nor do they have self-
learning capabilities. Anything you do to change airflow, fuel, spark or
timing in attempt to make more power will always require re-mapping of
the ECM and testing.
Today there are many options offered by aftermarket manufacturers that
can completely retrofit and replace old outdated MEFI 1 thru 3 systems.
Holley, FAST and Mallory all offer complete marine fuel injection kits that
are far better than what was originally installed on marine engines back
in the 1990s. I believe that the system offered by FAST is my top pick for
ease of installation for both the do-it-yourselfer and service shops. The big
benefit of all of these systems is that they are self-learning so you don’t
need an ECM with a specific program mapped for your specific engine.
This means it can compensate for engine modifications. This alone is a
huge bonus for a boat owner looking to upgrade their performance level.
When doing engine modifications on an EFI engine, make sure you
find a good service source that has all the capabilities to perform not
only the engine mechanical
upgrades, the engines
ECM upgrades, and
dynamometer testing.
In my next article I will
delve deeper into the marine
electronic fuel injection
system. Thanks for reading.
.
FAST Marine
EFI controller
Photos top to bottom: MerCruiser 350 HO MAG MPI fuel injection MEFI 3;
MerCruiser 320 EFI; Volvo Penta Throttle body injected using MEFI 3;
MerCruiser HP 575 SC using MEFI 3.
.
Performance new engine MPI using MEFI 3.
.
