Installation Manual

Chapter 4 N40475
Page 12
Part dry, part wet systems
Even where the engine is mounted well below the waterline
the advantages of a wet system can still be gained, providing
that water injection takes place at a point sufciently above
the waterline.
In these circumstances the part dry, part wet system
shown in gure 5 can be utilised. The modular exhaust
components allow a system to be readily constructed,
utilising a tall dry riser, followed by a water injection elbow.
(1) Stainless steel bellows.
(2) Optional high rise extension - not factory supplied.
(3) Flexible hanger.
(4) Point of water injection to be 200mm (8 inches) minimum
height above water line.
(5) 5
O
minimum average fall.
(6) Water line.
Water lift systems
Figure 6 shows the main features of such a system, which
utilises pressure developed by the exhaust gases to
force a mixture of gas and water to a height which may
be considerably above the engine. When the engine is
stopped the exhaust tank contains the water which falls
back from the exhaust riser.
If a proprietary unit is used the manufacturers instructions
should be carefully followed, but gure 5 identies the key
features.
(1) Exhaust tank (water lock).
(2) Water injection elbow.
(3) To overboard outlet.
(4) 1/2” bore siphon break.
(5) Top of exhaust riser and point at which the siphon break
is connected to the engine pipe work must be above the
water line under the worst possible conditions (normally
a distance of 450mm (18”) under static conditions will be
sufcient)
(6) Exhaust riser.
Note: that the system must meet the requirement for
the maximum exhaust back pressure to be not greater
than 15kPa, measured within 305mm (12 inches) of the
turbocharger/ exhaust outlet. Minimum volume of exhaust
tank should be 3 times the volume of the water in the riser.
The tank should be installed near the centre-line of sailing
craft.
Figure 5
Figure 6