Answer
Finding bottom-end/connecting rod bolts slack during a routine 500-hour inspection is an extreme emergency that could have caused a crankcase explosion or engine destruction.
Immediate Outage: Lock out the auxiliary engine. Do not turn or run it under any condition.
Destructive Inspection: Dismantle the affected bottom-end bearing assembly completely. Inspect the crankpin journal surface for scoring, ovality, and cracks using Non-Destructive Testing (NDT) like Dye Penetrant.
Bolt & Bearing Replacement: Discard all the affected connecting rod bolts and nuts. Never re-torque a bolt that has run slack due to fatigue or thread deformation. Replace the bottom-end bearing shells entirely, checking the serrations on the connecting rod palm for fretting or distortion.
Investigate Installation Root Cause: Review the maintenance records from the last major overhaul. Check whether the correct hydraulic tightening pressures or torque parameters were used, and if a calibrated torque wrench/hydraulic pump was utilized.