Why Engine Load Matters — Protecting Performance and Longevity
Every modern diesel engine is designed to deliver exceptional power and reliability, but only when operated within its safe performance range. Understanding engine load — the percentage of total available power being used — is key to maintaining efficiency and protecting your investment.
Understanding Engine Load
Marine diesel engines, such as Volvo’s D-series paired with IPS drives, are capable of running at full power but are not designed to do so continuously. Manufacturers like Volvo recommend keeping the maximum continuous load below 85%. Exceeding that threshold for long periods can accelerate wear and cause costly damage.
Sustained operation above 85% load increases the risk of:
Turbocharger overheating and premature failure
Excess crankcase pressure and blow-by
Fuel injector stress and over-fuelling
Fuel dilution in engine oil
Shortened engine life and higher maintenance costs
High-load operation (85–100%) is acceptable for short bursts — typically no more than five minutes at a time.
How to Monitor Engine Load
Modern Volvo EVC (Electronic Vessel Control) systems display real-time engine load (%) for each engine directly on the helm screen, making it easy to ensure both remain within safe limits. During normal cruising, aim to keep each engine below 85% load.
If you’re unsure where to find the load display or how to interpret it, check your onboard system manual or ask your service team for a quick walkthrough.
Why Fuel Use, RPM, and Speed Still Matter
While engine load provides the most accurate measure of engine effort, RPM and speed don’t tell the full story. Load can fluctuate dramatically depending on:
Sea state and wind conditions
Vessel weight and onboard load
Hull and propeller cleanliness
Trim and running attitude
For instance, your engines might show 85% load at 2,200 RPM in calm water on a clean hull, but 95% load at the same RPM in rough conditions or with marine growth on the hull.
That’s why it’s important to regularly monitor:
Engine load (%)
Fuel flow (L/hr)
Trim and vessel response
Best Practice
Keep both engines below 85% load during regular cruising.
Avoid full-throttle operation unless necessary.
Adjust trim to optimise efficiency and reduce unnecessary fuel burn.
By keeping engine load in check, you’ll enjoy better performance, lower fuel costs, and longer engine life — ensuring smoother, safer, and more efficient time on the water.