Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 145Get this manual
Connecting Rods 1Check connecting rods for alignment by placing rods
on surface plateIf light can be seen under any portion of machined surfacesif rod has slight wobble on plale, or if 0.002 in(0.051mm) feeler gauge can be inserted between any machined surface and surface plate, rod is bent and must be discarded2OverheatingOverheating is visible as bluish bearing surface color that is caused by inadequate lubrication or excessive RPM
SpallingSpalting is the loss of bearing surfaceand it resembles flaking or chippingSpalling will be most evident on the thrust portion of the connecting rod in line with the beamGeneral bearing surface deterioration could be caused by or accelerated by improper lubrication
aSpalling
3RustRust formation on bearing surfaces causes
uneven pitting of surface(s)