Mercury INSTALLATION MANUAL D7.3L D-TRONIC - Manual (Page 13)

D7.3L D-TRONIC DIESEL ENGINES - BRAVO MODELS
Page 13 of 90
4. The tank breather pipe must have an inner diameter of at least 1/2 in. (13mm) and must
be fitted with a swan neck to prevent water from entering the tank.
It is recommended that the exact route and length of the fuel lines be established at the first
installation of the engine to prevent problems later in connecting them to the engine.
All fuel lines must be well secured. The holes where the lines run through the bulkheads
should be carefully rounded off, or protected with rubber grommets. This prevents damage
to the lines from abrasion.
FUEL CONNECTIONS
The following, but not limited to the following, additional fuel connection related points, ap-
plying to all engines unless otherwise stated, must be considered [Refer to boating stan-
dards (NMMA, ABYC, etc.) and Coast Guard regulations for complete guidelines]:
1. Fuel pickup should be at least 1 in. (25mm) from the bottom of fuel tank, to prevent pick-
ing up impurities.
2. Fuel supply lines must not be smaller than 3/8 in. (11 mm) I.D. tube for V8 model. A fuel
return line between engine and fuel tank is required, for all models the return line must
not be smaller than 5/16 in. (8 mm).
3.
On Multi-Engine Installations:
Use a separate tube for the fuel supply line and fuel
return line for each engine.
4. Larger diameter (than previously specified) lines, and fittings must be used on installa-
tions requiring long lines or numerous fittings.
5. Fuel line(s) should be installed free of stress and firmly secured to prevent vibration and/
or chafing.
6. Sharp bends in fuel lines should be avoided.
7. A flexible fuel line must be used to connect fuel supply line to fuel inlet fitting on engine,
to absorb deflection when engine is running. Injection pump fuel return line must also
have a flexible rubber hose segment.
DIESEL FUEL FILTERS AND FUEL ADDITIVES
There is the possibility that contamination of diesel fuel and algae growth in the diesel fuel
could cause the blockage of the lift pump resulting in poor performance.
IMPORTANT: The engine is provided with an element type fuel filter, but to help elimi-
nate water and dirt it is recommended to use an additional 10 micron, 60 gal/min. (227
L/min.) flow rated filter that has a water trap.
It is recommended that in MerCruiser Diesel applications, an additional fuel filter equipped
with a water trap be installed before the lift pump. MerCruiser recommends a 10 micron, 60
gallon per minute (227 L/min.) rated filter, such as a Racor Model 500  (Quicksilver Part
Number 35-850481 with SAE threads, and 35-809867 with Metric threads) or equivalent.
This will help to filter out contaminants in diesel fuel.
Select a suitable position in the fuel system between the fuel feed pump and the fuel tank
for the additional filter The position selected must be free from vibrations, and allow for easy
inspection and replacement.
It is also recommended that a diesel fuel additive be added (to combat algae growth) particu-
larly in warmer climates. Additives reduce the chances of algae growth in the diesel fuel.