USCG Exam PracticeMaintenance, machine tools, drawings, and tables
A water-lubricated rubber stern tube bearing is being inspected. Under 46 CFR, at what point must it be rebushed?
- A. When diametral clearance reaches 6.4 mm regardless of shaft size
- ✓ When any water groove is worn to half its original depthCorrect
- C. When the Officer in Charge, Marine Inspection determines it necessary based on manufacturer recommendations
- D. When weardown is 1.6 mm less than the clearance limit applicable to the shaft diameter
Why B is correct
46 CFR §61.20-23(b) specifically addresses water-lubricated rubber bearings and requires rebushing when any water groove is half the original depth. The diametral clearance limits in §61.20-23(a) apply to non-rubber water-lubricated bearings, and the OCMI discretion standard in §61.20-23(c) applies to oil-lubricated bearings.
Cited:46 CFR §61.20-23