USCG Exam PracticeBearings, lubrication, and care of machine parts
According to 46 CFR, when must the after stern tube water-lubricated bearing (non-rubber) be rebushed on a vessel with propelling machinery located amidships, if the tailshaft diameter is 254 mm (10 in)?
- ✓ When clearance reaches 7.95 mm (0.3125 in)Correct
- B. When clearance reaches 6.4 mm (0.25 in)
- C. When clearance reaches 9.53 mm (0.375 in)
- D. When clearance reaches 6.35 mm (0.25 in) less than original
Why A is correct
46 CFR §61.20-23(a)(1) sets the rebushing threshold for shafts exceeding 229 mm (9 in) but not exceeding 305 mm (12 in) in diameter at 7.95 mm (0.3125 in) clearance for machinery located amidships. A 254 mm shaft falls within that range.
Cited:46 CFR §61.20-23