3–22 Chris-Craft
Systems
Engine Instruments
You should become familiar with “normal” gauge readings for your engines and become accustomed to
scanning the instruments when running. Unusual instrument readings require immediate attention. Do not
ignore unusually high or low instrument readings. Shut down the engine and have the problem diagnosed
before operating the engine.
Figure 3-19. Dual Engine Trim Switches
Tachometer
The tachometer (tach) indicates the revolutions per minute (RPM) of the engine. Important
RPM’s to note from the manufacturer’s engine manual include idle RPM, normal cruise RPM
and maximum RPM. The maximum RPM should not be exceeded.
Although tachometers do not indicate boat speed, a careful helmsmen will chart boat speed vs.
RPM so that, in the event of other electronics problems, he will have a very good idea of boat
speed from his tachometers.
A sudden change of RPM may indicate a problem within the engine or a problem with the drive
train or running gear. Do not ignore “unexplainable” changes in RPM. A simple check of the
engine and running gear may prevent costly repairs.
Speedometer Read in miles and kilometers per hour. Indicates speed of the boat.
Oil Pressure
Gauge
The oil pressure gauge measures the pressure of the lubricating oil circulating through the
engine. Adequate oil pressure is required to pump oil into the many highly-loaded bearings that
require lubrication. Inadequate oil pressure can lead to excess wear and possibly catastrophic
failure of the engine.
Check the manufacturer’s engine manual to determine normal oil pressure for the engines in
your boat. Shut down and do not operate an engine that has had a loss of oil pressure.
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