USCG Exam PracticeMaintenance, machine tools, drawings, and tables
For a vessel with propelling machinery located AFT, at what clearance must the after stern tube bearing (water lubricated, non-rubber) be rebushed when the shaft diameter is 200 mm (approximately 7.9 inches)?
- A. 6.4 mm (0.25 in)
- B. 7.95 mm (0.3125 in)
- ✓ 4.8 mm (0.1875 in)Correct
- D. 9.53 mm (0.375 in)
Why C is correct
46 CFR §61.20-23(a)(1) sets the amidship-machinery limit for shafts 229 mm or less at 6.4 mm (0.25 in). §61.20-23(a)(2) requires rebushing 1.6 mm (0.0625 in) less than that limit when machinery is located aft, giving 6.4 minus 1.6 = 4.8 mm (0.1875 in).
Cited:46 CFR §61.20-23