GASOLINE ENGINES BRAVO MODELS
Page 17 of 116
THROUGH THE TRANSOM OR HULL EXHAUST
NOTICE
Refer to Exhaust Resonators in this SECTION for additional information on 454 and
502 cid (7.4 L and 8.2 L) engine exhaust requirements.
When designing and installing an exhaust system, in addition to other model specific
requirements, Mercury MerCruiser requires the following to be observed:
• Exhaust fittings (flanges and outlets) must be of proper size to accommodate 4 in.
(102 mm) inner diameter exhaust hoses.
• Exhaust fittings must be equipped with internal water shutters.
• An exhaust flapper must be used over each outlet.
• Exhaust outlet must be slightly above the water line with boat at rest in the water and
a full load aboard.
• Exhaust hoses, collectors and pipes must not be higher than exhaust elbows at any
point.
• The drop in the exhaust system must be continuously sloping so that a low spot does
not exist at any point in the exhaust hose or pipe.
• The exhaust system on Mercury MerCruiser engines must have a minimum of 6°
downward slope between the exhaust elbow outlet and the exhaust outlet of the boat.
• The exhaust system on Mercury MerCruiser engines must have a minimum of 4 in.
(102 mm) of vertical drop between the exhaust elbow outlet and the exhaust outlet
of the boat.
75203
a
b
c
d
e
Example Of Sterndrive (MCM) Through The Transom or Hull Exhaust Models
a-Minimum Continuous Exhaust System Slope
b-Exhaust Hose
c-Exhaust Fitting
d-Flapper
e-Exhaust Elbow
f-Minimum Exhaust System Vertical Drop
• Back pressure must not exceed 2 psi (14 kPa) when measured at exhaust elbow
outlets.
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