If you want to get all crazy about it...... They also sell spacer blocks to raise your elbows up if you need to


1. Fill all fuel, water, gray water and heater tanks to maximum capacity.
NOTE: Weight can be added in these locations to simulate full loaded condition.
2. Add maximum allowable cargo weight to boat in areas where it will be stowed, including
refrigerator and lockers.
3. Add 190 lb (86 kg) of weight in all locations where each passenger will sit during normal
operation.
4. Measure exhaust elbow height. Also, measure exhaust system slope on applications
with through the hull or through the transom exhaust.
75203
72429
a
b
Using A Universal Protractor (Inclinometer) To Measure Slope
a - Protractor
b - Exhaust Hose Or Tube
5. Follow instructions a. or b.:
a. On applications with through the propeller exhaust: Proceed to Step 6.
b. On applications with through the hull or through the transom exhaust:
(1.) Move load weight to bow to simulate greatest “bow-down” attitude the boat will
encounter in normal operation.
(2.) Recheck exhaust system slope.
(3.) Proceed to Step 6.

6. On all applications:
a. Move load weight and cargo weight to stern of boat to simulate greatest “stern-down”
attitude the boat will encounter such as when loading.
IMPORTANT: Be sure to consider swim platform loading and PWCs.
b. Recheck exhaust system measurements.
7. Measurements must be equal to or greater than, the following:
On All Applications:
Minimum Exhaust Elbow Height from Top of Elbow to Waterline
Model Measurement
All V6 and V8 13 in. (330 mm)
71533
a
b c
d
MCM 454/502 MPI Engine Shown (All V-6 and V-8 Engines Similar)
a - Top Of Transom
b - Highest Point On Exhaust Elbow
c - Measurement
d - Waterline
Additional Requirements for Through The Hull and
Through The Transom Exhaust System Applications:
Minimum Continuous Downward Slope (Exhaust Hoses, Collector, Etc.)
Model / Application Measurement
All Sterndrive 6°

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
c b
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

I'm Doing The Same..........does Anyone Have An Opinion On Tips Specifically Gil's With Welded Baffels Vs. With Flaps.
Going On A Stock 7.4 Mpi ....any Performance Issues