POWERHEAD
90-826883R2 JUNE 1998 Page 4-29
4. Water Marks: Whenbearing surfaces aresubjected to watercontamination, a bear-
ing surface “etching” occurs. This etching resembles the size of the bearing.
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5. Spalling: Spallingisthe loss of bearingsurface,andit resembles flaking orchipping.
Spallingwill bemostevident onthethrustportionoftheconnectingrodinlinewiththe
“I” beam. General bearing surface deterioration could be caused by or accelerated
by improper lubrication.
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a - Spalling
6. ChatterMarks: Chattermarksare theresultof a combination oflowspeed-low load
- cold water temperature operation, aggravated by inadequate lubrication and/or im-
proper fuel. Under these conditions, the crankshaft journal is hammered by the con-
necting rod. As ignition occurs in the cylinder, the piston pushes the connecting rod
with tremendous force, and this force is transferred to the connecting rod journal.
Sincethereislittleorno load on the crankshaft, itbounces awayfrom theconnecting
rod. The crankshaft then remains immobile for a split second until the piston travel
causestheconnectingrodtocatchuptothewaitingcrankshaftjournal,thenhammers
it. The repetition of this action causes a rough bearing surface(s) which resembles a
tinywashboard.Insomeinstances,theconnectingrodcrankpinborebecomeshighly
polished. Duringoperation, the engine will emit a “whirr” and/or “chirp” sound when it
is accelerated rapidly from idle speed to approximately 1500 RPM, then quickly re-
turned to idle. If the preceding conditions are found, replace both the crankshaftand
connecting rod(s).
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a - Chatter Marks Between Arrows
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