Exhausts And Mounting Exhausts - Beta Marine Beta 43 Operator's Maintenance Manual

Exhausts
(a) An engine correctly installed in accordance with this
handbook will meet the emission requirements of the
RCD (see page 64).
(b) Keep dry exhaust systems to a minimum length and have
swept bends (NOT right angle elbows). Exhaust back
pressure is increased by longer exhaust length and sharp
bends. Back pressure should be measured; with the
complete exhaust system connected and the engine
running at full speed; and should NOT exceed 62 mm
Hg (2.4 inches Hg). The correct measuring point is before
the injection bend (at the manifold flange).
Typical Yacht Exhaust Installation
Warning
(1) One of the most common problems with engine
installations (and possibly expensive), is water entering
the engine exhaust manifold from the exhaust system by
syphoning when the engine is switched off. This can
occur when the point of water injection "X" on the engine
is close to or below the water line. Water entering the
pistons can cause bent con rods, emulsified engine oil
and a wrecked fuel pump! It's best avoided!
6
Maximum Seawater level
when heeled (measured on
the centre line of the boat)
Normal Seawater Level
40 cm
minimum
5 cm
minimum
Propeller Clearance:
between tip of propeller blade and underside
of hull should be at least 10 percent of the
propeller blade diameter
Wet Exhaust hose should be matched to the injection
bend sizes detailed below.
Exhaust Beta 43
Standard 50 mm
High rise water 50 mm
injection bend SS
Cross over water 50 mm
injection bend SS
(2) This diagram shows a typical exhaust installation.
The rubber hose connecting the heat exchanger to the
injection bend must be replaced by a hose (a) of
sufficient length, connecting to a "T" piece or anti-syphon
valve that is above the maximum seawater level when
heeled (at least 30 cms / 12 inches above the water line)
on the centre line of the boat. The pipe then returns to
the injection bend and the seawater is pumped down the
exhaust pipe.
(3) The exhaust back pressure should NOT exceed
62 mm Hg (2.4 inches Hg).
30 cm
minimum
Waterlock
Silencer
If a rope cutter is fitted, allow approximately 1/2"
for movement of engine, see manufacturer's literature
7
Beta 50 Beta 60
50 mm 50 mm
50 mm 50 mm
50 mm 50 mm
Anti syphon valve or
T piece fitted here
a
X