, Training for Mariners. The First with Online Study for the Maritime Industry.

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The subjects listed below are currently available for testing in the new online study room and are available for download to your computer. Click on subject below for details.

Engineering Examination Questions

All Engine Room Questions

Engine Room Electrical         

Engine Room General          

Engine Room Safety            

Engine Room Steam            

Engine Room Motor   

QMED Oiler          

Deck Examination Questions

Master 25/50/100 Ton

Operator Uninspected Passenger Vessel

All Deck Questions

Able Seaman Questions

Advanced Subjects, Unlimited Oceans Master, Mate

Rules of the Road  

Aids to Navigation  Glossary Included

Breathing Apparatus

Cargo Equipment 

Cargo Stowage

Charts and Publications 

Chemical Testing

Right Whales

Damage Control  

Deck Engineering

Deck Safety

Emergency Procedures 

FCC Exam Questions

Fire Fighting Glossary Included 

First Aid  


Great Lakes

Hazardous Cargo

Inert Gas

Inland Navigation  

Instruments and Accessories



Liquid Cargo and Bunkering

Marine Radio Operator 

Meteorology  "Glossary Included" 

Mobile Offshore Drilling Unit

Latest NMC / USCG Questions

Celestial Navigation

Navigational Procedures

Pollution Control and Prevention

Rules and Regulations

Plotting/Navigational Problems


Survival Craft

Seamanship   Glossary Included

Sailing Vessels  

Ship Handling 

Ships Construction Glossary Included  

Ships Business


Stability and Trim Glossary Included 


Tides and Currents Glossary Included 



Common Knots

Radar Plotting



Sample Solution for a Free Surface Correction Problem 

The SS AMERICAN MARINER is ready to bunker with drafts of FWD 15'-05", AFT 21'-03". After all bunkers are on board, soundings indicate the tonnages shown.

Use the white pages of The Stability Data Reference Book to determine the free surface correction.

A. 1.05 feet


B. 1.15 feet


C. 1.25 feet


D. 1.31 feet



Step 1:

Calculate Mean Draft.

15'-05"fwd + 21'-03" aft = 36'08"

Mean Draft: 36'-08"/2

Mean Draft = 18'04"

Step 2:

Using the Hydrostatic Properties table (Sheet 3) for the SS American Mariner (White Pages), calculate the Total Displacement (S.W. Tons) for the vessel before loading bunkers with a mean draft of 18'04".

The table yields 12,000 tons as the displacement of the vessel at 18'04" mean draft.






Step 3:

Add up all the bunker totals for each tank. The sum of all bunkers equals 3024.8 tons.

Step 4:

Add the displacement of the vessel before loading the bunkers and the sum of all the bunkers to find the ship's final displacement.

12,000 tons + 3024.8 tons = 15024.8 tons

Step 5:

Refer to the Table for Free Surface Correction and Tank Capacities (Sheet 4) to calculate the free surface moment for each tank. On the S.S. Mariner , a tank is considered FULL if the tank is at least 97% full. Any quantity less than 97% full or an empty tank is considered SLACK.

In the column F.O. Tons under Tank Capacity, the table gives you the capacity of each tank at 97% full. This is the column you will compare your loaded bunkers in each tank with to verify if a tank is considered FULL or SLACK. For example, DB 1 CL is loaded with 48.2 tons of bunkers. The tank capacity at 97% for D.B. 1 CL is 48.2 tons. Therefore, the tank is considered FULL and its free surface correction is 67. Conversely, D.B. 4 CL is loaded with 208.6 tons of bunkers. The tank capacity at 97% for D.B. 4 CL is 224.1 tons. Since 208.6 tons is less than 224.1 tons then D.B. 4 CL is considered SLACK.

Now find the free surface moment for each tank.

Next, find the total sum of free surface moment which equals 17,309 foot tons.

Step 6:

Find the free surface correction in feet by dividing the total free surface moment by the

final displacement of the vessel.

FS(corr) = 17,309 foot tons/15,024.8 tons

FS(corr) = 1.15 feet


Last edited on 12-May-2020 18:55:22 -0400

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Revised: 12 May 2020 18:55:22 -0400 

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For details on license requirements, application forms,  licensing fees, and testing locations, visit the United States Coast Guard / National Maritime Centers web site and look under Mariner's information center. The questions used in the online study are once again available to the public in PDF format from the NMC link above. The illustrations are not yet available for some of these questions.

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See also:

SeaSources online Celestial Navigation Course 

MARYLAND NAUTICAL  Great source for practice charts and study guides


National Oceanic & Atmospheric Administration (NOAA)

The Navigation Center

Chart No. 1 Nautical Chart Symbols Abbreviations and Terms

Bluewater Books and Charts 

Search CFR'S Online

Open Book Renewals

Required Subjects for all Deck Licenses

Required Subjects for all Engineering Licenses

Required Subjects for Mobile Offshore Drilling Units, MODU.

Sea Service Requirements for Coast Guard Licenses