Spare parts decisions can seem straightforward at the time. But their real impact often emerges later: under load, over time or during audits. Which common choices could be quietly increasing your vessel’s lifecycle risk – and what should you do differently?
Spare parts decisions often seem low risk when they are made, but the real consequences of these decisions only emerge later.
Consequences like increased wear, system incompatibility or even component failure may only appear under sustained operating load, during audits or after system modifications. The people managing the impact might not even be the people who made the original decision about which spare parts to buy.
In practice, the safest spare parts decisions are those that remain predictable, traceable and explainable long after installation. For example, choosing genuine OEM spare parts reduces your operational risk because genuine parts ensure verified compliance and predictable performance in your real-life operating conditions, now and in the future.
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Wärtsilä’s Hannu Puputti, Senior Product Manager, often sees the negative results of inadvisable spare parts decisions in his work. Based on patterns he’s seen repeated across many different real maritime operations, here are five decisions ship owners and operators are making that can quietly increase lifecycle risk.
Why this decision feels safe at the time
It is easy to think that if a part fits and has similar specifications, it should work. A replacement part may have the right dimensions, look like the part you’re replacing, install correctly and allow the system to restart. This can feel like a successful outcome, but fit does not equal predictable system behaviour over time.
What can change later
Even if a part fits and works on day one, a lot of things can change over time. Small variations in tolerances, materials or surface treatments mean parts may behave differently under real operating conditions. These differences can mean problems like faster wear rates, poor sealing performance or even damage to other components. These effects are not always immediate. They often build gradually until other components are affected or maintenance intervals shorten unexpectedly.
Where the risk shows up
Premature wear may lead to unplanned downtime. Unexpected sealing performance, temperature fluctuations or increased vibration rates can also lead to downtime, or equipment damage over time. When issues emerge later, you can find it very hard to get to the bottom of the problem through root cause analysis.
A spare part that fits is not necessarily safe – small differences can cause wear, failure and costly downstream damage over time.
Hannu’s expert insights:
“In spare parts, ‘it fits’ is not the same as ‘it will behave as planned over time’. The real test comes under operating load, temperature variation and wear. That is where small differences can become expensive.
“Parts in existing installations might be modified several times during the lifecycle of the installation. When the decision is made to use a cheaper alternative, the link to the latest version of the part designed for that specific engine is lost. In one case, a customer had purchased a piston that fit the engine perfectly, but it failed after just a dozen hours of operation, causing severe damage to the engine block and necessitating replacement of the crankshaft. The root cause of the incident was the non-OEM piston, which had mechanical and chemical properties that were nowhere near Wärtsilä’s standard.
“The only way to ensure parts are compatible with your current engine specification is to buy them through the OEM’s identification system, which is based on unique serial numbers and engine-specific version management.”
The easiest way to ensure you buy the latest version of the correct part for your vessel is through Wärtsilä Online. Here’s how:
Why this decision feels safe at the time
When you’re in a hurry to make a fix and keep your vessel on schedule, a part that can arrive quickly may feel like it’s worth more than one with verified compatibility. Spare parts decisions are often made under pressure – during port stays, maintenance windows or unplanned events. In these situations, it’s understandable to prioritise availability over verified compatibility.
What can change later
Non-verified parts installed because of time pressures often cause headaches later. Over time, mixed component histories develop, making future maintenance and troubleshooting far more complicated than it should be. System performance may quietly drift without a clear cause.
Where the risk shows up
An incompatible part can lead to repeated interventions, inconsistent performance and a greater maintenance need, even without a single identifiable failure. This can increase day-to-day costs, with patterns showing why only becoming visible after extended periods of time.
Choosing the fastest available part without verified compatibility can shift risk into ongoing performance issues and higher lifecycle costs.
Hannu’s expert insights:
“When a vessel is under scheduling pressure, the fastest available part can feel like the safest decision. But if you haven’t verified the compatibility of that part, you could just be shifting the risk from today’s delivery window into tomorrow’s troubleshooting and maintenance costs.”
Why this decision feels safe at the time
In a market flooded with lookalike parts and AI-generated claims, a cheaper alternative can seem like an attractive option. If you pick a part that has certification labels and claims of equivalence, it’s understandable that you’d feel confident in your choice. The short-term cost looks attractive and at first glance the part appears to meet the same standards. But can you be sure the claims are accurate?
What can change later
While two parts may look the same, the performance of ‘equivalent’ parts will probably not be what you expect. You might see differences in fatigue resistance, wear characteristics or tolerance levels; there might be issues with how the part interacts with other components. Documentation gaps appear and accountability becomes unclear when something fails. It turns out ‘equivalent’ wasn’t equivalent after all.
Where the risk shows up
Equivalence is hard to prove after a part has been in use. It can be hard to troubleshoot problems or failures because the behaviour of ‘equivalent’ parts is not predictable. In incident reviews, warranty discussions and insurance and compliance assessments, when something has gone wrong it can be difficult to establish the facts or prove the specifications were the same.
Parts labelled as ‘equivalent’ may meet specifications on paper but can introduce unpredictable performance and compliance risks over time.
Hannu’s expert insights:
“Equivalence claims can look convincing on paper, but lifecycle performance is proven in operation. If you can’t verify how a part performs over years of service, you’re accepting uncertainty into a system.
“Recently, the UK’s Marine Accident Investigation Branch (MAIB) highlighted the dangers of using substandard components in vessel engines. The offshore vessel Kommandor Susan was in sea trials when it suffered a catastrophic engine failure, which resulted in an engine room fire and a complete power blackout. With no propulsion the vessel started to drift, and the crew couldn’t deploy the anchors to stop it because they needed electrical power.
“The MIAB established that the engine failure was caused by the premature wear of bearings that had been fitted during a major overhaul – bearings that were not approved by the engine’s OEM and exhibited weaker material bonding than genuine parts.”
Why this decision feels safe at the time
Your part works and the system runs. As long as your vessel maintains its schedule, records can be sorted out later. Spare parts decisions are often made under pressure – when a part is marketed as OEM equivalent it’s easy to assume that documentation is in order.
What can change later
Over time, that missing documentation can become very important. Your crew may change and your system might undergo upgrades. Regulatory scrutiny is increasing too – accurate and comprehensive records are becoming more important. Without consistent documentation, it becomes impossible to track what was changed, when and why.
Where the risk shows up
During audits and compliance checks, without complete documentation you and your teams will be unable to explain exactly what’s changed in your system, when it was changed and whether a particular component has the required specification. The part may not have failed, but it creates risk because you may not be able to explain the service history with confidence. This can happen years after purchase.
Missing documentation may not affect performance immediately, but it creates serious risk in audits, compliance checks and future maintenance.
Hannu’s expert insights:
“Documentation often feels like an afterthought until you need to explain exactly what was installed, when it was changed and whether it meets the required specification. In my experience, traceability is not paperwork overhead; it is part of operational risk control.
“Think of it this way: traceability is the mechanism that connects the spare part to the equipment’s current and future state. By ensuring you have correct documentation you both know, and can prove, compatibility now and in the future. This is especially valuable in long-life assets where documentation, modification history and configuration control are essential to maintaining reliability and regulatory compliance.”
Why this decision feels safe at the time
Ship equipment is complicated, whereas thinking on a component level is simpler and often more familiar. A specific issue can be addressed and improvements seem isolated, with no trade-offs immediately visible.
What can change later
Vessel systems don’t operate in isolation, and interactions between components and systems often cause unintended effects. Performance gains in one area can have negative impacts elsewhere.
Where the risk shows up
Over time you run the risk of reduced system reliability, recurring issues that are hard to diagnose and increasing operational uncertainty. Problems will often feel disconnected because no single component seems responsible for the problems you are experiencing.
Optimising individual components instead of system behaviour can reduce overall reliability and create problems that are difficult to diagnose.
Hannu’s expert insights:
“A vessel doesn’t operate as a collection of isolated parts. When you change one component, the effects can show up somewhere else later. That is why the safest decisions are made with system behaviour in mind, not just individual component cost or availability.”
The five decisions above are not unreasonable – or unusual. They can be seen frequently in real maritime operations, even in well-run fleets, because they are often made under pressure and with the best of intentions.
Reducing your vessel’s lifecycle risk depends on three things:
This is where original equipment manufacturer (OEM) expertise and system knowledge matters. Choosing OEM spare parts is the safest choice because the OEM is best positioned to understand how a part will behave inside your specific vessel system – on the day it is installed and far into the future.
About to make a spare parts decision for a critical system?
Use this checklist to verify compatibility, traceability and lifecycle risk.
Most spare parts decisions won’t have an immediate negative effect on equipment operation. Decisions are made with the best of intentions, but the risk is in the loss of predictability. What does this mean in practice?
Spare parts decisions are more than just a purchasing choice; they’re about minimising long-term operational risk and maintaining optimised performance over time. The safest spare parts decisions are those that solve your problems today – and that you can still explain and document five years later.
IMO-regulated engine parts play a direct role in maintaining compliance with NOx emission requirements under MARPOL Annex VI. For IMO-regulated engine components, spare parts decisions are more than just maintenance decisions. Compliance must be treated as a critical purchasing criterion to avoid operational risk.
Using non-genuine IMO parts can create problems that emerge later during audits, troubleshooting or future maintenance work. Incomplete traceability, uncertain specifications or undocumented changes can make it harder to verify compliance, explain system history or maintain predictable engine performance over time.
Many workshops can also refuse to perform service work on parts where the origin, specification or compliance status cannot be verified. In practice, this can create delays and operational disruption if non-genuine components are discovered during maintenance or troubleshooting activities.
Buying from OEMs such as Wärtsilä is the safest and most reliable choice for IMO-regulated spare parts because these components always come with:
Purchasing genuine OEM parts means you have one accountable partner for the parts themselves, technical support, documentation, troubleshooting and lifecycle services. This:
The five spare parts decisions outlined above may seem reasonable in the moment. But over time, they all reduce one critical factor: predictability. The safest spare parts decisions are those that remain predictable, traceable and explainable throughout your vessel’s lifecycle – not just at the time of installation.
The five decisions that increase operational risk when buying spare parts are:
In practice, reducing lifecycle risk comes down to three things: verified compatibility, full traceability and system-level understanding. This is why choosing genuine OEM parts is the most reliable way to ensure consistent performance, compliance and long-term cost control.
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All quotes in this article were provided by Hannu Puputti, Senior Product Manager, Wärtsilä Marine.
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