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13. Installation Instructions
Sharp bends should be avoided.
Exhaust hoses should be connected straight on the riser
outlets.
Exhaust back pressure test should be preformed to
ensure that exhaust components are adequately sized.
Exhaust back pressure should be between 1-3 PSI.
Some back pressure is necessary to prevent water
intrusion. Do not go below 1 PSI.
Exhaust risers must be the suggested distance above
the water line. Install riser spacers if necessary.
A minimum of 18” of exhaust hose must be installed
between the exhaust risers and the collector, Y-pipe,
muffler or first angular fitting. This portion of the
exhaust hose must have a downward slope of 1-1/4”/
ft. for conventional inboards and a downward slope
of 7/8”/ft. for V-drives. Some OEM installations may
different from these specifications but these installa-
tions have been carefully evaluated by MARINE POWER
and the OEM.
After the first 18” the exhaust system must have a drop
of 1/2”/ft. Measure exhaust riser height as shown.
Minimum exhaust riser height should be 15” on 6.0 and
6.2L engines. All others should be 13”.
The slope in the exhaust hose and components must
be routed so that no low point exists in the system
where water may be retained. The muffler, collector and
exhaust hoses must be adequately supported for
proper routing and to prevent over stressing the exhaust
manifolds and risers.
Internal flappers may be required on naturally aspirated
6.0 and 6.2L engines.
Applications with through transom exhausts must be
equipped with exhaust flappers to prevent the reverse
flow of water into the engine. Exhaust outlets should be
above the water line with the boat at rest to minimize
engine back pressure.
Every exhaust connection should be secured with at
least 2 hose clamps. The clamps should be stainless
steel and at least 1/2” wide.
Electrical Connection
NOTE: Marine Power EFI engines are equipped with
“Smart Start” this feature is common in late model
automobiles but is new to the boating industry. This
feature enables the operator to start the engine by
momentarily engaging the key switch, it is not
necessary to hold the key switch. The ECM maintains
the starter engagement until the engine starts. Once
the engine starts, the ECM prevents the starter from
engaging even if the operator mistakenly turns the key
switch. To ensure proper operation of this feature, the
engine wiring harness includes an 18 gauge wire coiled
by the starter. This wire must be connected directly to
the battery or the battery switch. Do not connect this
wire to the starter post as the voltage drops excessively
at this location during starting.
Batteries
Tapered post connections with wing nut connections
can be used. The tapered posts must be used for the
engine battery cables while the wing nut connections
should only be used for accessories. We highly recom-
mend that wing nuts be replaced with regular nuts to
increase the tightness of the connections.
Pay particular attention to ground connections. EFI
engines are very dependent on secure ground connec-
tions. See typical ground location.
Dual Engines
Batteries: Vessels with twin engines should have a
battery for each engine. The battery switch should be
positioned so each engine is running off its own battery.
Battery Isolators
Many boats are equipped with auxiliary batteries. Such
batteries are used to operate stereos, etc. Battery
isolators can be used to charge an auxiliary battery. In
these cases, the alternator output is connected to the
center post on the isolator instead of the starter. The
owner should familiarize himself with the isolator’s
operation.
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