Installation Manual

N40475 Chapter 7
Page 21
Figure 2
Typical fuel systems
The more simple the fuel system, the better it will
perform in service. Figure 1 shows an ideal system.
1. Fuel tank.
2. Fuel return pipe.
3. Manual fuel feed.
4. Stop cock.
5. Vent.
6. Drain.
In some applications there may be legislation that
requires that fuel lines draw from, and return to ,
the top of the tank. Figure 2 shows an acceptable
arrangement.
1. Fuel tank.
2. Fuel return pipe.
3. Manual fuel feed.
4. Vent.
5. Fuel feed tap.
6. Drain tap
The fuel tank may be steel, aluminium, or G.R.P. or,
alternatively, a rubber bag tank may be used. The
main fuel connection is taken from the rear of the tank
so that all the fuel is available for use when under way
when the hull will be at an angle. The fuel return is
extended within the tank to near the bottom in order
to prevent air locks which can arise due to siphoning
of the fuel when the engines are stopped.
The fuel lines may be of metal, either copper or ‘bundy’
steel tubing used either with compression ttings or
preferably soldered nipples, with a exible armoured
rubber hose to connect to the primary fuel lter.
This simple fuel system is satisfactory when one or
more engines are run from a single fuel tank, and
it may also be used when there are two tanks each
supplying one engine. In the latter case the system
may include a cross connection, between the tanks by
means of a balancing pipe, with a valve, at each end.
In some installations cross connecting pipes between
the two engine feed pipes and the two engine return
pipes have been used, but valves are necessary
in every line so that the appropriate system may
be selected, and the complexity of installation and
operation is such that the advantages in operating
exibility are out-weighed by the possibility of obscure
problems due to component malfunctions, incorrect
operation or engine interaction.
Figure 1