USCG Exam PracticeMaintenance, machine tools, drawings, and tables
Under 46 CFR §61.20-23, when must a water-lubricated rubber stern tube bearing be rebushed?
- A. When diametral clearance reaches 6.4 mm regardless of shaft size
- ✓ When any water groove is half the original depthCorrect
- C. When the Officer in Charge, Marine Inspection determines it is necessary
- D. When weardown is 1.6 mm less than the clearance limit for amidship machinery
Why B is correct
46 CFR §61.20-23(b) specifically states that water-lubricated rubber bearings must be rebushed 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; the OCMI determination in (c) applies to oil-lubricated bearings.
Cited:46 CFR §61.20-23