USCG Exam PracticeBearings, lubrication, and care of machine parts
For a vessel with propelling machinery located amidships, at what maximum clearance must the after stern tube water-lubricated (non-rubber) bearing be rebushed if the tailshaft diameter is 254 mm (10 inches)?
- ✓ 7.95 mm (0.3125 in)Correct
- B. 6.4 mm (0.25 in)
- C. 9.53 mm (0.375 in)
- D. 1.6 mm (0.0625 in)
Why A is correct
46 CFR §61.20-23(a)(1) specifies that for shafts exceeding 229 mm (9 in) but not exceeding 305 mm (12 in) in diameter with machinery located amidships, the after stern tube bearing must be rebushed at 7.95 mm (0.3125 in) clearance. A 254 mm shaft falls within that range.
Cited:46 CFR §61.20-23(a)(1)