According to 46 CFR Subpart 61.20 regarding...

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Question 1 of 205eccefa1bacbc34ba4d4717f

According to 46 CFR Subpart 61.20 regarding the periodic tests of machinery and equipment, what is the maximum tail shaft to stern tube bearing clearance (at the after end of the stern tube) that would require rebushing for a vessel in ocean service, with an aft propulsion machinery space, a 14" diameter tail shaft, and a water lubricated stern tube bearing constructed of material other than rubber?

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🔍 Key Concepts

• Review 46 CFR 61.20 table for tail shaft to stern tube bearing clearances, focusing on water-lubricated bearings and materials other than rubber. • Pay attention to how the regulation changes limits based on shaft diameter (in inches) and service type (e.g., ocean service) and machinery space location (aft propulsion machinery space). • Note that the CFR gives specific maximum allowable clearances before rebushing is required, often expressed as a fraction of an inch related to shaft diameter ranges.

💭 Think About

• First, identify the correct row in the CFR table for: water-lubricated, non-rubber bearing, ocean service, aft propulsion machinery, and a 14-inch tail shaft. Which diameter range does 14 inches fall into? • Once you find the correct row, look for the column that lists the maximum allowable clearance at the after end of the stern tube before rebushing is required. What exact fractional value is given there? • Compare the CFR value you found to the closest matching option in the multiple-choice answers. Are there any options that are clearly too small or too large compared to the regulation’s listed limit?

✅ Before You Answer

• Verify you are looking at 46 CFR 61.20-23 (or the specific section covering tail shaft clearances) and not a different machinery test requirement. • Confirm the bearing type: it must be water lubricated and made of material other than rubber; do not use the rubber-bearing limits by mistake. • Double-check the shaft diameter range in the table: make sure 14 inches is inside the correct bracket (e.g., "over X inches to and including Y inches"), so you read the right clearance value.

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