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SERVICE BULLETIN
DATE:
5/25/84
BULLETIN NUMBER: 139
MODEL:
All Propulsion and Generator Models
SUBJEC~
Hydro-Hush Muffler Installations
The illustrations shown with this text should be used as a guide when
making an installation of a Hydro-Hush Muffler.
When used in conjunction with a propulsion engine,
the Hydro-Hush
Muffler should be mounted close to the for-aft center line of the
boat.
When used with a generator unit, the muffler should be as close
as possible to the generator.
All installations should be such that the entry of water into the
engine exhaust manifold and cylinders is prevented while under sail
and at various angles of heel, from following seas, when backing down
or any other condition.
units installed with the exhaust manifold/water injected exhaust elbow
at or below the water line of the vessel must install a vent or syphon
break in the sea water
supply line to the water
injected exhaust
elbow.
The sea water supply line must be looped above the water line
a minimum of six inches (6") with the vent or syphon break installed
at the top of this loop.
The vented loop, when used, can be a mechanical syphon break as sho.wn
in the
illust~ation
or a simple tee arrangement with a small hose or
tube (3/16 - 1/4 inch I.D.) routed to the transom exhaust discharge or
to a separate thru-hull fitting located above the water line.
This
hose or tube must be routed in such a way that it will drain of water
when the engine is shut down and allow air into the sea water supply
hose and injection elbow.
The syphon break or vent is installed to break the vacuum in the sea
water cooling circuit and thereby discourage syphoning of sea water
through this circuit, and subsequent filling of the exhaust and engine
cylinders with sea water.
When used, syphon breaks should be checked
'-.
-'
periodically for proper operation and should be installed in a loca-
,j
tion where, should they leak sea water, water would not leak onto the
engine or its accessories.
The Hydro-Hush Muffler remains approximately 30 percent full of water
after engine shutdown when there is a maximum of 48 inches of lift on
the discharge side.
Continued ••••••••••••••••••••••
110
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