PRODUCT OVERVIEW
12
JH Series Operation Manual
New Engine Break-In
As with all reciprocating engines, the way
your engine is operated during its first 50
hours of operation plays a very significant
role in determining how long it will last and
how well the engine will perform over its
lifetime.
A new YANMAR diesel engine must be
operated at suitable speeds and power
settings during the break-in period to make
the sliding parts, such as piston rings,
break-in properly and to stabilize engine
combustion.
During the break-in period, the engine
coolant temperature gauge should be
monitored; temperature should be
between 71° and 87 °C (160° and 190 °F).
During the first 10 hours of operation, the
engine should be run at maximum engine
speed minus 400 to 500 min
-1
(approximately 60 to 70% of load) most of
the time. This will ensure the sliding parts
break in properly. During this period, avoid
operating at maximum engine speed and
load to avoid damaging or scoring sliding
parts.
NOTICE
Do not operate at WOT (wide open
throttle) for more than a minute at a time
during the first 10 hours of operation.
Do not operate the engine at low idle or at
low speed and light load for more than
30 minutes at a time. Since unburned fuel
and engine oil will adhere to the piston
rings when operating at low speeds for
long periods, this will interfere with proper
movement of the rings and the engine oil
consumption may increase. Low idle
speed does not allow break-in of sliding
parts.
If operating engine at low speed and light
load, you must race the engine to clean the
carbon from the cylinders and fuel injection
valve.
Perform this procedure in open waters:
• With the clutch in NEUTRAL, accelerate
from the low-speed position to the
high-speed position briefly.
• Repeat this process five times.
Once past the initial 10 hours until 50
hours, the engine should be used over its
full operating range, with special emphasis
on running at relatively high power
settings. This is not the time for an
extended cruise at idle or low speed. The
boat should be run at maximum speed
minus 400 min
-1
most of the time
(approximately 70% load), with a 10
minute run at maximum minus 200 min
-1
(approximately 80% load) every
30 minutes and a 4 to 5 minute period of
operation at WOT (wide open throttle)
once each 30 minutes. During this period,
be sure not to operate your engine at low
speed and light load for more than
30 minutes. If operating engine at low
speed and light load by necessity, just after
the low idle operation, be sure to race the
engine.
To complete engine break-in, perform
After Initial 50 Hours of Operation
maintenance procedures.
Hours of Operation on page 117
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