Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 241Get this manual
Connecting Rods 1Check connecting rods for alignment by placing rods on surface plateIf light can be seen under any portion of machined surfaces, if rod has slight wobble on plate, or if 0.002 in(0.051 mm) feeler gauge can be inserted between any machined surface and surface plate, rod is bent and must be discarded2Overheating: Overheating is visible as bluish bearing surface color that is caused by inadequate lubrication or excessive RPM3Rust: Rust formation on bearing surfaces causes uneven pitting of surface(s)
5Spalling: Spalling is the loss of bearing surface, and it resembles flaking or chippingSpalling will be most evident on the thrust portion of the connecting rod in line with the "I" beamGeneral bearing surface deterioration could be caused by or accelerated by improper lubrication
51853Spalling
51853Pitting