GENERAL - 7A-190-823225--1 1096
Exhaust System
Requirements
IMPORTANT: It is the responsibility of the boat
manufacturer or installing dealer to properly lo-
cate the engine and install the exhaust system.
Improper installation may allow water to enter the
exhaust manifolds and combustion chambers
and severely damage the engine. Damage
caused by water in the engine will not be covered
by MerCruiser Limited Warranty, unless this
damage is the result of defective part(s).
Determining If Exhaust Elbow Risers
Are Required
On all engines to determine if exhaust elbow risers
are required, take measurements (a) and (b), with
boat at rest in the water and maximum load aboard.
Subtract (b) from (a). If (a) minus (b) is less than spe-
cified in chart, select appropriate size exhaust elbow
riser kit and exhaust extension kit that will correctly
position exhaust elbow.
72700
Exhaust Elbow Measurement
a - From Waterline To Top Of Transom
b - From Highest Point On Exhaust Elbow To Top Of Transom
Model
(a) Minus (b) Must Be
at Least
All 13 In. (330 mm)
MCM (Stern Drive) Engines With Thru
Transom Exhaust
When designing and installing exhaust system, the
following must be observed:
Minimum Hose Size
Model Single Outlet Dual Outlet
All 4 in. (102 mm) 3 in. (76 mm)
1. Exhaust flanges must be of proper size to accom-
modate 4 in. (102 mm) I.D. exhaust hoses. They
must also be equipped with internal water shut-
ters, and use an exhaust flapper over each outlet.
2. The exhaust hoses and pipes must not be higher
than exhaust elbows at any point.
3. The exhaust outlet must be located so that a mini-
mum of 1/2 in. (13 mm) drop per foot (305 mm)
downward pitch exists in the exhaust hose from
the engine exhaust elbow to the outlet. (This is an
American Boat & Yacht Council recommenda-
tion.) The drop must be constant so that a low
spot does not exist at any point in the exhaust
hose.
4. Exhaust outlet must be slightly above the water-
line with boat at rest in the water and full load
aboard.
5. Back pressure must not exceed 4 in. (102 mm) of
mercury when measured with a mercury manom-
eter to exhaust elbow outlets.
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