Maritime Knowledge Base
Browse questions and answers across marine machinery, merchant navy careers, shipboard operations and maritime glossary terms.
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Marine Machinery
Troubleshooting guides for pumps, boilers, purifiers, compressors and auxiliary systems.
Merchant Navy Careers
Questions about joining the merchant navy, exams, cadetships, ranks and sea-time.
Maritime Glossary
Plain-English definitions of shipping, engine-room, navigation and regulatory terms.
Shipboard Operations
Practical Q&A for watchkeeping, safety, maintenance routines and onboard documentation.
Results for "Bearing"
What is a thrust bearing or thrust block and what does it do?
The thrust bearing, or thrust block, absorbs the forward or astern thrust developed by the propeller and transmits it to the ship's hull, so the thrust actually drives the ship.
Marine MachineryWhat is a bearing and what types are used in marine engines?
A bearing supports and locates a rotating shaft while allowing it to turn with little friction — marine engines rely on plain white-metal bearings lubricated by an oil film.
Marine MachineryWhy is the main engine lubricating oil pressure low?
Low lubricating oil pressure is a serious alarm that threatens the bearings — the cause is usually in the pump, the filters, the oil itself, or a leak.
Marine MachineryWhat is the stern tube and stern tube seal on a ship?
The stern tube is the tube through which the propeller shaft passes out of the hull; it carries the aft bearing and a seal that keeps seawater out and lubricant in.
Marine MachineryWhat causes a crankcase explosion in a marine engine?
Crankcase explosions are caused by oil mist igniting after a hotspot overheats the lubricating oil — understanding the mechanism is key to preventing them.
Marine MachineryWhat causes a marine engine turbocharger to surge?
Turbocharger surging is a violent, audible instability of the airflow through the compressor — it signals a mismatch between the turbocharger and the engine's demand.
Marine MachineryHow does a marine diesel engine work?
A marine diesel engine converts the chemical energy of fuel into rotary motion through compression ignition — here is the working principle and the two-stroke and four-stroke cycles.
Shipboard OperationsWhat is the procedure for anchoring a ship?
Anchoring safely means preparing the gear, approaching the chosen spot slowly against wind and tide, letting go with controlled cable, and keeping an anchor watch.
Shipboard OperationsWhat are the four stages of passage planning (appraisal, planning, execution, monitoring)?
Passage planning follows four stages — appraisal, planning, execution and monitoring — that together prepare and carry out a safe voyage from berth to berth.
Marine MachineryHow does a marine engine turbocharger work?
A turbocharger uses the energy of the engine's exhaust gas to drive a compressor that forces more air into the cylinders, greatly increasing power and efficiency.
Shipboard OperationsHow does marine radar and ARPA work?
Marine radar detects other ships and land by transmitting radio pulses and timing their echoes; ARPA automatically tracks targets and calculates the risk of collision.
Marine MachineryWhat is cylinder lubrication in a two-stroke marine engine?
Cylinder lubrication is the separate oil supply fed onto the liner of large two-stroke engines to lubricate, neutralise fuel acids and keep the surfaces clean.
Shipboard OperationsWhat is dead reckoning in navigation?
Dead reckoning is estimating a ship's present position from a known past position by applying the course steered and the distance run, without reference to external fixes.
Shipboard OperationsHow do you read a nautical chart?
A nautical chart is a map of the sea showing depths, dangers, aids to navigation and the coastline, read using its scales of latitude and longitude, soundings, symbols and compass rose.
Marine MachineryHow does a ship's steering gear work?
The steering gear is the powered hydraulic machinery that turns the rudder in response to helm orders from the bridge, using rams or rotary vanes driven by pumps.
Marine MachineryHow does a marine centrifugal pump work?
A centrifugal pump moves liquid by spinning it with an impeller, which throws the liquid outward and converts its speed into pressure — the most common type of pump aboard ship.
Marine MachineryWhat is the difference between a controllable-pitch and a fixed-pitch propeller?
A fixed-pitch propeller has blades set at one permanent angle, while a controllable-pitch propeller can rotate its blades to vary thrust and go astern without reversing the engine.
Marine MachineryWhat is scavenging in a two-stroke marine engine?
Scavenging is the process of pushing the burnt exhaust gases out of a two-stroke engine cylinder and replacing them with fresh air, ready for the next combustion cycle.
Marine MachineryWhat is an indicator diagram and what does it tell the engineer?
An indicator diagram plots the pressure inside an engine cylinder against volume or crank angle, letting the engineer assess the power, condition and faults of each cylinder.
Marine MachineryWhat is a reduction gearbox on a ship and why is it used?
A reduction gearbox lowers the high rotational speed of a medium- or high-speed engine to the slower speed that turns an efficient propeller, and can combine several engines onto one shaft.
