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Six weeks on a distant fishing ground, a loaded ocean crossing, a research vessel working a survey area for thirty days, a service vessel that stays on the wind farm all winter: in every one of these cases the ship sails with what she will have until she comes back. No delivery at anchor, no express freight, no technician joining at the next port, because there is no next port.

The question changes shape. It is no longer at what stock level do we reorder, but what do we load before we let go the lines. That is a single decision, taken alongside, with no second chance. Whatever is not in the store room at departure will not exist for the whole voyage, however good the supplier catalogue is and however urgent the need becomes.

The general method for running MRO stock — criticality ranking, safety stock, reorder point, tied-up capital, the split between ship and shore — is covered in our article on MRO inventory management and critical spare part stockouts. This article is the limiting case of that method: the one where replenishment disappears as a variable. Everything below follows from that.

What Is Not On Board Does Not Exist

Three hundred miles from the nearest coast, a part being in stock at a supplier has no operational value whatsoever. The ship's store is the only store. That obvious statement has three consequences that are routinely underestimated until you have lived through a breakdown mid-voyage.

No express freight, no technician

Getting a part out to a ship at sea is still theoretically possible, but it needs a means: a support vessel, a supply ship passing through, a helicopter within range, another company vessel on a track through the same area. Every one of those options is expensive, weather dependent, and often simply unavailable. The engine builder's service engineer, meanwhile, does not step aboard at sea. His support is limited to whatever fits down a satellite phone line or an email, at the bandwidth of the day and across a time difference.

Deviation is the only real fallback

When a part is missing and the failure cannot wait, the remaining option is to deviate to a port. On a fishing trip that means several days steaming each way, the fishing days lost with them, and usually the loss of the ground being worked. On a survey voyage it means measurement windows that cannot be recovered: the weather window or the observation season does not come round again until next year. The real cost of a deviation is never the fuel burnt, it is the value of the mission lost.

The failure gets repaired with what you have

The third effect is the insidious one. Without the right part, the crew improvises: a gasket cut from sheet, a bearing of roughly the right size, an electrical bypass, a piece of equipment isolated and worked around. Those fixes sometimes hold until the ship is back alongside, and that is a credit to the engineers. But they create technical debt that has to be written down somewhere, or it resurfaces six months later during a class survey or a port State control inspection. An undocumented temporary repair is a dormant non-conformity.

How to Build the Spare Parts Loadout List

A loadout list is not built by working through a parts catalogue. It is built by starting from the consequences of a failure and working down in layers.

First layer: what endangers the ship or the crew

The ISM Code requires, at paragraph 10.3, that equipment and technical systems whose sudden operational failure may result in hazardous situations are identified, and that specific measures are taken to promote their reliability. On a ship trading coastwise, that list mainly frames the preventive maintenance and the periodic testing of stand-by arrangements. On a long voyage it becomes, directly, page one of the loadout list. A piece of equipment identified as critical under 10.3 for which no spare is carried is not merely a debatable logistics call: it is an inconsistency inside the safety management system.

In practice: propulsion and its control, electrical generation and its emergency back-up, steering gear, fire fighting, bilge and drainage, navigation and communication equipment. For each of them, the question is not whether it can fail, but if it fails halfway through the voyage, what do I repair it with, how long does it take, and who does it.

Second layer: what stops the mission without endangering the ship

A trawler with the main winch out of action is still fully manoeuvrable, and no longer fishing. A research vessel with a seized A-frame steams perfectly well and puts nothing in the water. A service vessel whose gangway motion compensation has failed makes port safely and transfers nobody. This equipment does not always appear on the ISM critical equipment list, but its failure cancels the whole point of the voyage. On a long trip it deserves the same treatment as the main engine.

Third layer: degraded operation and habitability

Then comes everything that neither sinks the ship nor sends her home: a fish hold refrigeration plant, a service air compressor, a secondary hydraulic power pack, a freshwater generator, sewage treatment, a washing machine, an oven. Over three days you do without. Over six weeks, a failed freshwater generator or a fish hold that no longer holds temperature changes the nature of the voyage. On a long trip, crew comfort is not a luxury: it drives fatigue, and fatigue drives safety.

The decision grid, part by part

Every candidate for the loadout goes through the same questions. The answer is not always yes; what matters is that it is explicit and written down somewhere.

This grid does not produce a score. It produces a reasoned decision, which is a very different thing: when the ship comes back, each decision can be tested against what actually happened.

Space, Weight and Tied-Up Capital

There is no ideal list, because three physical and financial limits bound it at all times.

The store room has a finite volume

On a thirty metre trawler, the ship's store is a cramped compartment, sometimes no more than a set of lockers and boxes split between the engine room and a forepeak. You do not stow a spare crankshaft in it. The volume limit forces a choice between the component-level spare, which takes little room but implies a longer job, and the complete assembly, which swaps out fast but eats the store. On a research or service vessel there is more room, but it is contested by mission equipment, deck containers and provisions.

Weight loaded is never free

The weight of spares counts twice. It counts for stability and trim: a few tonnes of parts stowed high or badly distributed show up in how the ship behaves, and an owner who adds weight without declaring it is working against his own stability booklet. It also counts for consumption and deadweight: capacity given over to spares is capacity not given to catch, cargo or bunkers. Finally, a heavy item badly secured becomes a projectile in a seaway. Securing is part of the decision to load a part, not just part of executing it.

The capital sails with the ship

A part put on board is capital tied up that will not come back before the end of the voyage. That is not an argument for loading less, it is an argument for loading accurately. A spare turbocharger that sleeps through three voyages in a row raises a legitimate question, and the answer may perfectly well be: we keep it, because not having it would cost the entire trip. What is not acceptable is failing to ask. This connects directly to how the vessel maintenance budget is built, where the voyage spares line should be identified in its own right and defended as such.

Long Lead Time, Made to Order, Single Source

Some parts are not decided in the week before sailing. They are decided months ahead, because the time needed to obtain them is far longer than any technical port call.

Long procurement lead times

Liners, pistons, shaft bearings, gearbox components, controllable pitch propeller parts, winch shafts, large A-frame bearings: these items are not on a shelf. The lead time quoted by the engine builder or the deck machinery maker is often measured in weeks, sometimes in months, and transport and customs clearance stretch it further. If a wear interval falls due during the voyage, the order must be placed against the running hours projected to the end of the voyage, not against today's counter reading. Running hours tracked against the maintenance plan give exactly that: which intervals will fall due at sea, and which can wait for the ship to come back.

Made to order and single source

A part manufactured on demand — a machined bush, a reground shaft, a bespoke wiring loom, a moulded seal — has no stock to draw on: production starts when the order lands. A single-source part stacks up the risks: the supplier out of stock, a change of revision, a discontinued range, or simply a manufacturer unavailable at the wrong moment. For both families you need the real observed lead time, not the commercial one quoted in the brochure, and you need to know whether a second source exists. That information is gathered calmly between voyages, never under pressure.

Electronic obsolescence

PLC cards, electronic governors, variable speed drives, engine control units: their commercial life is shorter than the life of the ship. A spare card bought today may not exist in a few years, or may only exist in a version incompatible with the software on board. For a ship going far, the spare card is not just a part, it is insurance against obsolescence — provided someone periodically checks that it still matches the revision of the installed system, and that the configuration is backed up on board.

Repair On Board or Replace the Whole Unit

Two philosophies live side by side in every store room. Carry component-level spares and repair the failed item. Or carry complete assemblies, swap them out, and land the removed unit for overhaul ashore. The right choice depends on the ship and her crew, not on a general doctrine.

The component-level spare

O-rings, gaskets, diaphragms, valves, springs, mechanical seals, bearings, wear rings, pump overhaul kits: small, cheap, and they cover the large majority of jobs actually carried out. Their limit is time and skill. Rebuilding a screw pump from a full kit needs an engineer who has done it before, an up to date sectional drawing, a clean bench and several hours during which the system is down.

The complete assembly

An injector assembled and pressure tested, a complete cylinder head, a complete pump, a spare electric motor, an electronic card, a complete hydraulic ram: remove, refit, service restored in a fraction of the time. Cost and volume are higher, but availability is immediate and the job depends far less on fine craft skill. On a long voyage with a small engine department that argument carries real weight, particularly at night and in a seaway.

Three questions settle it

Skill on board: who in the department can do this job at sea? Tools: is the puller there, the torque wrench covering the right range, the bearing heater, the dial gauge, the injector test bench? Time: can the equipment stay down for the length of the repair, or does service have to be restored within two hours? Those three answers differ from ship to ship for the same equipment. That is why a loadout list copied from another vessel never works as it stands. A properly written maintenance job plan already answers much of it: it lists the parts, the tools and the time the job takes.

A frame to work through, system by system

The table below is not a list to copy. It is a review grid, to check that no system has been forgotten before the list is frozen.

Tools and Consumables: The Part Alone Is Not Enough

A part without the tool that fits it is an ornament. This is the most common and the most avoidable mistake in a loadout list.

Special tools

Pullers and hub extractors, timing tools, torque wrenches that genuinely cover the range specified, impact wrenches, bearing heater, portable press, dial gauge and feeler set, hose crimping tool, injector test bench, insulation tester, clamp meter, a thermal camera if the ship uses one. Every one of these has to be checked working before departure, not assumed present. A timing tool lent to another vessel and never returned always comes to light at the worst possible moment.

Consumables

Engine and gearbox oils to the exact specification, hydraulic oils, greases, coolant and its inhibitors, water treatment chemicals and their test reagents, refrigerants, loose O-rings by size, stainless and high tensile fasteners, terminals, sleeving, clips, sealants and threadlock, degreasers, absorbents, rags, welding rods kept dry, cutting discs, welding gas. It is a thankless list, nobody gets excited about it, and it is the list that most often stops a job dead.

A consumables holding is sized on the length of the voyage and on what was actually used on previous voyages, not on a hunch. It is one of the few families where the arithmetic is straightforward, provided the issues were recorded in the first place. Add the consumables of diagnosis: oil sampling bottles, water circuit test reagents, recording media. A sample taken at sea and analysed on return is usually worth more than a diagnosis improvised offshore.

Mandatory Spares and SOLAS Expiry Dates

Part of the list is not the chief engineer's to judge. It is imposed, and its absence is a non-conformity rather than an operational choice.

Spares required by class and flag

Classification societies define, for certain notations and ship types, a minimum outfit of spare parts for the main machinery and essential auxiliaries. The flag State may add requirements of its own. These parts are not traded off against space or capital: they are verified present, correct and identifiable. On a ship running an approved planned maintenance system, the consistency between the plan, the required spares and the actual holding is part of what the surveyor comes to look at.

SOLAS safety equipment and its dates

Hand flares, parachute rockets, smoke signals, EPIRB batteries, hydrostatic release units, liferaft servicing, breathing air cylinder testing, extinguishers, immersion suits, medical stores: all of it carries a date. On a voyage of several weeks those dates must be projected across the length of the trip, not simply read on the day of departure. Pyrotechnics that expire on day ten leave the ship non-compliant for the rest of the voyage, with no way of putting it right.

The working rule is simple: any date falling due during the voyage is dealt with before sailing. Any extension is a matter for the flag State or the classification society, is requested alongside, and cannot be improvised from offshore. The same logic applies to the ship's certificates and to the crew's certificates, whose renewal depends on shore-side formalities.

Shelf Life and Ageing in the Store Room

A part loaded is not a part preserved. A ship's store is a hostile environment: salt air, condensation, temperature swings between the engine room and an unheated compartment, constant vibration, impact in a seaway. Some families cope badly with that, and a degraded part discovered in the middle of an emergency is exactly equivalent to a part that was never loaded.

Ageing is managed by rotation. A part bought for one voyage and not used sails again with a known age; after a certain number of voyages it comes out of the active holding and is renewed, even if it looks new. That means knowing the date each item entered stock, which no handwritten notebook holds for long and which a spreadsheet loses at the first crew change.

Stowage and Retrieval: A Part You Cannot Find Is a Part You Do Not Have

A ship can load exactly the right part and then fail to find it. At sea, with a small crew and a breakdown in progress, an hour spent opening boxes is an hour lost. After two hours the team concludes the part is not on board and improvises. The result is identical to having forgotten it, with the purchase cost on top.

A stowage plan, not a memory

The store is divided into zones, racks and bins, physically identified. Every item has a location, and that location is written down. A chief engineer who knows his store by heart is not an organisation: he is a single point of failure who signs off one day and takes the plan with him.

Marking that survives the environment

Labels that stay legible, resist oil and damp, with text that does not wipe off at the first pass of a rag. The marking carries the part number, the description and above all the equipment it belongs to. A supplier reference on its own means nothing to somebody looking for the seal off the port sea water pump. Putting a QR code on bins and equipment removes the manual lookup and goes straight to the item record, with its quantity and its location.

Linking parts to the equipment register

This is what separates a ship's store from a stack of boxes. Every item is linked to one or more pieces of equipment on board. You can then answer the only question that matters during a breakdown: for this pump, what do I have on board, how many, and where exactly? Without that link, people search by supplier reference, find nothing, and buy again what was already sitting in the store.

The Pre-Departure Review: Real Stock, Not Theoretical Stock

Theoretical stock is what the system says. Real stock is what you can put your hands on. The gap between the two always shows up at the worst moment, unless somebody goes looking for it deliberately before sailing.

Count, open, verify

Before a long voyage the inventory is not a declaration. Critical items are physically counted. Doubtful packages are opened: a seal kit broached during an earlier job and put back on the shelf is a classic trap, and it does not show from the outside. Each stocked reference is checked against the installed equipment, serial number and modification revision included — two engines of the same type do not always take the same part. Finally, expiry dates are read against the length of the voyage, not against today's date.

The review needs more than one voice

The list is read through with the chief engineer and, depending on the ship, the second engineer, the bosun for deck machinery and the superintendent ashore. Each of them sees what the others do not: the person who runs the plant knows its real weak points, the person who follows the fleet knows what ran short on the other ships. The review produces three useful outputs: the approved list, the list of deliberate and recorded omissions, and the list of orders to place immediately.

Tools and documentation belong in the review

At the same time you confirm that the special tools are on board and working, that manuals, sectional drawings, wiring diagrams and parts catalogues are available offline, and that job procedures can be consulted where they will actually be needed, which is in the engine room and not from a desk ashore. The satellite link of a ship on passage guarantees nothing: anything essential has to be available locally.

Debriefing the Voyage: This Is What Writes the Next List

The loadout list for one voyage is written by the voyage before it. That only works if somebody recorded what actually happened, while it was still fresh.

Seven findings, seven decisions

On return, you sort. The exercise takes half a day and is worth more than any theoretical stock calculation.

Without a written history, nothing is handed on

This debrief is only worth something if it is attached to the equipment concerned and kept. A chief engineer who holds it all in his head does excellent work while he is on board, and resets the counter to zero the day he signs off. A history kept in a CMMS where every stock issue is linked to a work order and to a piece of equipment produces, as a by-product, the real consumption per voyage, per equipment and per ship. That data, and nothing else, allows the next voyage to be sized by something better than guesswork.

Sister Ships: Pooling Experience Across the Fleet

An owner running several identical vessels has an advantage that few actually use: every failure suffered by one ship is free information for the others.

Pool the experience before pooling the stock

If ship A has broken the same winch bearing twice in two voyages, ships B and C should be carrying it, whether or not they have met the problem themselves. That requires the information to travel by something other than conversation on the quayside: a shared register, equipment named the same way from one ship to the next, comparable histories. That is precisely what fleet-wide management delivers, where the same equipment carries the same designations everywhere.

Pool the stock, but carefully

When voyages are not simultaneous, an expensive and rarely used item can be held once for several ships, provided it is alongside at the right moment and can reach the vessel before she sails. That reasoning works for staggered rotations; it collapses the moment two ships sail in the same week. Pooling is decided on the operating schedule, not on the parts catalogue.

Beware of drift between hulls

Sister ships delivered together diverge over time: retrofits, replacement by successor models, different modification revisions, an auxiliary changed on one ship only after a failure. A fleet loadout list therefore has to stay broken down by hull, with the real serial numbers of each machine. The part from the sister ship that will not fit is a mild irritation alongside, and an unrepaired failure at sea.

From a List to a Method

Loading for a long voyage is not filling a store room. It is taking, alongside, a series of reasoned decisions about what can break, what the crew will be able to repair at sea, and what you accept in advance you will not be able to repair. The quality of those decisions depends far less on the individual experience of the chief engineer currently in post than on the memory of the company: past consumption, past failures, the lists from previous voyages and what was missing from them.

The general principles — criticality, thresholds, tied-up capital, the split between ship and shore — remain the ones set out in our article on MRO inventory management. A long voyage does not change that logic: it removes the safety net. That is what makes it demanding, and that is what makes the written history indispensable.

91�鶹��Ʒ links the ship's store to the equipment register, to work orders and to purchase requests, so that every part issued feeds the history that will be used to prepare the next voyage. To talk it through against your own operation, get in touch.

Building the onboard stock relies on consumption history, which we discuss in the maritime CMMS guide.