The engine of any piece of equipment is taken
for granted as long as it runs smoothly and
efficiently. But all engines lose power sooner or
later from normal wear. When this happens, the
mechanic must be able to determine the cause and
know what is needed to correct the trouble.
Generally speaking, it is not the supervisors
job to perform engine repairs, but it is the
supervisors job to see that these repairs are
performed correctly and to assist and instruct
those doing the work.
Since the SEABEEs use many models of
internal combustion engines, it is impossible to
specify the detailed overhaul procedures for all
the engines. However, here are several basic
principles that apply to all engine overhauls.
1. Consult the detailed repair procedures
given in the manufacturers instruction and
maintenance manuals. Study the appropriate
manuals and pamphlets before attempting any
repair work. Pay particular attention to
tolerances, limits, and adjustments.
2. Observe the highest degree of cleanliness
in handling engine parts during overhaul.
3. Before starting repair work, be sure all
required tools and replacements for known
defective parts are available.
4. Keep detailed records of repairs, such as
the measurements of parts, hours of use, and new
parts installed. An analysis of these records will
indicate the hours of operation that may be
expected from the various engine parts and help
in determining when a part should be renewed to
avoid a failure.
Since maintenance cards, manufacturers
technical manuals, and various instructions
contain repair procedures in detail, this chapter
will be limited to general information on some of
the troubles encountered during overhaul, their
causes, and methods of repair.
HORSEPOWER AND HORSEPOWER
Horsepower is a unit for measuring work per
unit of time. One horsepower is equivalent to
33,000 foot-pounds of work per minute.
Horsepower is determined by either measuring
mechanically or computing mathematically.
Maintenance manuals should be consulted for
engine performance data and specifications. These
manuals will also have additional horsepower
designations and the many different horsepower
ratings used by manufacturers in describing the
equipment. The method used in measuring power
and the purpose for which it is intended account
for the variety of horsepower and horsepower
INDICATED HORSEPOWER is the theo-
retical power that an engine would deliver if all
frictional losses were eliminated. It is used mainly
by experimental engineers in designing new and
more efficient engines. Indicated horsepower may
be computed from the following formula:
Mean effective pressure in pounds
per square inch (This is the average
pressure on the piston during the
power stroke minus the average
pressure during the other three
Length of stroke in feet
Area of piston head in square inches
Working strokes per minute
Number of cylinders in the engine
of one horsepower