Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 62Get this manual
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cylinder, the piston pushes the connecting rod with tremendous force, and this force is transferred to the connecting rod journalSince there is little or no load on the crankshaft, it bounces away from the connecting rodThe crankshaft then remains immobile for split second, until the piston travel causes the connecting rod to catch up to the waiting crankshaft journal, then hammers itIn some instances, the connecting rod crankpin bore becomes highly polishedWhile the engine is running, "whirr" and or "chirp" sound may be heard when the engine is accelerated rapidly from idle speed to about 1500 rpm, then quickly returned to idleIf chatter marks are discovered, the crankshaft and the connecting rods should be replacedInspect the bearing surface of the rod and rod cap for signs of uneven wear and possible overheatingUneven wear is usually caused by bent connecting rodOverheating is identified as bluish bearing surface color and is caused by inadequate lubrication or operating the engine at excessive high rpmInspect the needle bearings, if installedA bluish color indicates the bearing became very hot and the complete set for the rod MUST be replaced, no questionService the connecting rod bearing surfaces according to the following procedures and precautions: a- Align the etched marks on the knob side of the connecting rod with the etched marks on the connecting rod capb- Tighten the connecting rod cap attaching bolts securely