---
kind: "range"
citation: "46 C.F.R. §§ 61.20-15–61.20-23"
title: "46"
from: "61.20-15"
to: "61.20-23"
count: 5
url: "https://uscodex.org/cfr/46/61.20-15..61.20-23"
---

# §61.20-15. Tailshaft examination.


The rules in [§§ 61.20-15 through 61.20-23](/cfr/46/61.20-15..61.20-23.md) apply only to vessels in ocean and coastwise service. Each examination, inspection and test prescribed by these sections must be conducted in the presence of a marine inspector.


# §61.20-17. Examination intervals.

- (a) A lubricant that demonstrates the corrosion inhibiting properties of oil when tested in accordance with ASTM D665 (incorporated by reference, see [§ 61.03-1](/cfr/46/61.03-1.md)) is considered to be equivalent to oil for the purposes of the tailshaft examination interval.
- (b) Except as provided in [paragraphs (c) through (f)](#c..f) of this section, each tailshaft on a vessel must be examined twice within any 5-year period. No more than 3 years may elapse between any 2 tailshaft examinations.
- (c) Tailshafts on vessels fitted with multiple shafts must be examined once every 5 years.
- (d) Tailshafts with inaccessible portions fabricated of materials resistant to corrosion by sea water, or fitted with a continuous liner or a sealing gland which prevents sea water from contacting the shaft, must be examined once every 5 years if they are constructed or fitted with a taper, keyway, and propeller designed in accordance with the American Bureau of Shipping standards to reduce stress concentrations or are fitted with a flanged propeller. Accessible portions of tailshafts must be examined visually during each drydock examination.
- (e) Tailshafts with oil lubricated bearings, including bearings lubricated with a substance considered to be equivalent to oil under the provisions of [paragraph (a)](#a) of this section need not be drawn for examination—
  - (1) If tailshaft bearing clearance readings are taken whenever the vessel undergoes a drydock examination or underwater survey;
  - (2) If the inboard seal assemblies are examined whenever the vessel undergoes a drydock examination or underwater survey;
  - (3) If an analysis of the tailshaft bearing lubricant is performed semiannually in accordance with the lubrication system manufacturer's recommendations to determine bearing material content or the presence of other contaminants; and
  - (4) **If—**
    - (i) For tailshafts with a taper, the propeller is removed and the taper and the keyway (if fitted) are nondestructively tested at intervals not to exceed 5 years; or
    - (ii) For tailshafts with a propeller fitted to the shaft by means of a coupling flange, the propeller coupling bolts and flange radius are nondestructively tested whenever they are removed or made accessible in connection with overhaul or repairs.
- (f) Tailshafts on mobile offshore drilling units are not subject to examination intervals under [paragraphs (b) through (d)](#b..d) of this section if they are—
  - (1) Examined during each regularly scheduled drydocking; or
  - (2) **Regularly examined in a manner acceptable to the Commandant CG-CVC.**

# §61.20-18. Examination requirements.

- (a) Each tailshaft must be drawn and visually inspected at each examination.
- (b) On tailshafts with a taper, keyway, (if fitted) and propeller designed in accordance with American Bureau of Shipping standards to reduce stress concentrations, the forward 1/3 of the shaft's taper section must be nondestructively tested in addition to a visual inspection of the entire shaft.
- (c) On tailshafts with a propeller fitted to the shaft by means of a coupling flange, the flange, the fillet at the propeller end, and each coupling bolt must be nondestructively tested in addition to a visual inspection of the entire shaft.

# §61.20-21. Extension of examination interval.


The Commandant CG-CVC may authorize extensions of the interval between tailshaft examinations.


# §61.20-23. Tailshaft clearance; bearing weardown.

- (a) Water lubricated bearings, other than rubber, must be rebushed as follows:
  - (1) Where the propelling machinery is located amidship, the after stern tube bearing must be rebushed when it is worn down to 6.4 mm (0.25 in) clearance for shafts of 229 mm (9 in) or less in diameter, 7.95 mm (0.3125 in) clearance for shafts exceeding 229 mm (9 in) but not exceeding 305 mm (12 in) in diameter, and 9.53 mm (0.375 in) clearance for shafts exceeding 305 mm (12 in) in diameter.
  - (2) Where the propelling machinery is located aft, the after stern tube bearing must be rebushed when weardown is 1.6 mm (.0625 in) less than the applicable clearance for propelling machinery located amidship.
- (b) Water lubricated rubber bearings must be rebushed when any water groove is half the original depth.
- (c) Oil lubricated bearings must be rebushed when deemed necessary by the Officer in Charge, Marine Inspection. The manufacturer's recommendation must be considered in making this determination.