MJM Yachts LLC 40z, Руководство пользователя

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Chapter 9 Finishes, Equipment, and Appliances MJM 40z Owner’s Guide page 35
9
APPENDIX
9.1 T
HE
T
OP
10 C
AUSES OF
E
NGINE
F
AILURE
It doesn’t happen often and if you’re familiar with
the common causes of engine failure you can cut
down on the chances of a breakdown. We want to
familiarize you with this list, compiled by
Motorboating Magazine (February 2006) and
embellished with a few MJM incidents. Here are
the Top Ten.
…R.I.J.
No Fuel
This is probably less of a problem on a
fuel-efficient MJM than on other boats, but lack of
owner attention to fuel consumption is the primary
culprit for engine failure. A boat’s fuel tank can be
nearly dry – even when the gauge claims there’s
1/4 of a tank left. This makes sense when you
realize that at cruising speed, the gauge shows the
tanks reading higher than when the boat is at rest.
A good rule is to not pass a fuel dock (no matter
the price) if your gauge shows less than 1/3 full.
Air in Fuel Line
If air gets drawn into the fuel lines
because of either a small leak in a fuel line
connection or the Racor Filter lid gasket/filter
basket tabs have interfered with the lid being
secured fully, you may find the engine will turn
over, but won’t start. Check the Racor to ensure
the fuel level is within an inch of the top. Check the
engine owner manual for the location of a manual
primer pump.
Dirty Fuel
Engine problems are caused by dirt and
water in the fuel. Debris, stirred up from the bottom
of the tank by wave action, is drawn into the fuel
line and clogs the fuel filter element. Starved for
fuel, the engine begins to run poorly, or won’t
reach proper RPMs. Water in the fuel can drive you
mad. Moisture condenses out of the highly humid
air on the inside walls of a fuel tank, then runs
down into the fuel. Water can also be introduced at
the fuel dock from a contaminated fuel supply. Fuel
floats on top of water and the fuel pick ups are
near the bottom of the tank. A Racor fuel/water
separator protects against this by handily extracting
the water. Check the bowl daily and drain off the
accumulated water. For severe contamination, use
a fuel-drying additive or have a diesel service
“polish” the fuel.
Fuel Bugs
Diesel engines suffer from microbial
bugs growing in the fuel. If left unchecked, these
critters clog filters. If you leave the same diesel fuel
in the tank for any length of time, a fuel conditioner
similar to that supplied with your boat by the builder
will kill the bugs and break up any hydrocarbon
residue into particles that will burn completely in
the combustion process.
Tired or Damaged Water Pump Impeller
As boats
age or if an engine isn’t operated for a long period
of time, a worn-out circulating water pump is
another engine killer. Impeller blades are commonly
made of a rubberized material that stiffens or
distorts over time and can break off entirely,
reducing coolant flow and clogging the heat
exchanger. Periodic engine maintenance
procedures can prevent this problem. A spare is
provided in the engine spares kit. Shown below is
an MJM 29z impeller that would have soon failed. It
was replaced during the 50-hour inspection on a
boat that had not been run for 11 months.
Another cause for impeller disintegration is running
the engine with the raw water intake shut off. By
the time that the overheating is discovered and you
shut down the engine, the impeller may already
have been destroyed or damaged. This happened
on a 34z when the operator forgot to be sure that
the raw water intake valve was in the proper
position.
Hard Hose
Another issue to be concerned about
with older boats. As water intake hoses age, they
lose their resiliency and collapse under suction,
causing a restriction in the flow of engine coolant.
This results in over-heating. Prevention is easy:
Visually inspect cooling hoses and squeeze them
to be sure they retain shape and set.
Clogged Raw Water Intake
The first clue may be
high or erratic Coolant Temperature readings on
one engine. This happened on a 50z when it
picked up a crab pot in Florida and the warp and
trap wrapped around the drive. Amazingly the