Debris in an engine’s lube oil system led to a diesel engine failure and an engine room fire aboard a passenger vessel docked in Portland, Maine, the National Transportation Safety Board (NTSB) said Tuesday (22 April).

The passenger vessel Ocean Navigator was moored at the Ocean Gateway Terminal on 18 October 2023, when the no. 2 auxiliary diesel generator engine suffered a catastrophic mechanical failure that seriously injured one crew member and resulted in an engine-room fire. Crewm embers secured ventilation to the engine room, and the fire self-extinguished. None of the 128 passengers onboard were injured, and no pollution was reported. Damage to the vessel was estimated at USD 2.4 million. 

After the fire, third-party technicians disassembled all components from the no. 2 auxiliary engine and found the crankshaft, several main bearings, connecting rod bearings and the no. 14 fuel injector were damaged. An additional inspection found abnormal wear on the connecting rod bearings and main bearings, which showed signs of cavitation erosion bearing damage, as well as damage from debris, which had been introduced at some point into the lube oil system.

NTSB investigators found the engine failure was caused by debris in the engine’s lube oil system—possibly due to the crew exceeding manufacturer-recommended intervals for changing the lube oil and oil filter elements—which caused catastrophic mechanical damage to the engine and a subsequent fire from the ignition of atomise lube oil released through the engine’s ruptured crankcase.

The crew had last changed the entire quantity of lube oil for the no. 2 auxiliary engine in September 2022—about 13 months before the engine failure—but the engine had operated more than 5,000 hours with this lube oil in the engine, five times longer than the manufacturer’s recommendation. Additionally, since the last change of the lube oil filter elements in May 2023, the engine had run over 3,000 hours. 

The engine manufacturer’s recommendation is to replace filter elements at every oil change or after the filter elements had been used for 1,000 hours.

“Manufacturers provide maintenance recommendations and intervals (schedules) to ensure equipment operates safely, optimally, and reliably throughout its service life,” the report said. 

“By regularly reviewing equipment manufacturer manuals and guidance, operators can ensure conformance with recommended maintenance plans and mitigate the risk of equipment malfunction or failure.” 

NTSB also found the crew’s quick action to secure engine room ventilation and engine fuel sources prevented the fire from spreading.

“Engine rooms contain multiple fuel sources as well as mechanical ventilation, making the spaces especially vulnerable to rapidly spreading fires,” the report said. 

“After an engine room fire ignites, it is imperative to remove the sources of available fuel and ventilation to the fire to prevent it from spreading. Vessel crews should familiarise themselves and train frequently on machinery, fuel oil, lube oil, and ventilation shutoff systems to quickly act to contain and suppress engine room fires before they can spread to other spaces.”

Note: Marine Investigation Report 25-13​ is available online.​

Photo credit: National Transportation Safety Board
Published: 24 April, 2025