NTSB: Not Following Maintenance Recommendations Led to Cruise Ship Fire

An explosion and fire aboard the coastal cruise ship Ocean Navigator in October 2023 was likely caused by not following maintenance recommendations and infrequent changes of lube oil and oil filters concluded the National Transportation Safety Board. One crewmember was seriously injured in an explosion and fire in the engine room of the ship when one of its auxiliary engines failed and parts were ejected during an explosion followed by a fire.

The Ocean Navigator, which was built in 2001 as a modern version of an American coastal cruise ship, was operating at the time for Hornblower’s American Queen Voyages and had just docked in Portland, Maine on its next to last scheduled cruise when the explosion occurred. Earlier in the year, AQY announced it would be removing the ship and her sister ship from service at the conclusion of the Canadian cruise season.

Engineers reported that the machinery was working properly as they navigated into the port and docked around 0630. There was a total of 210 people aboard, 128 passengers and 82 crewmembers. After shutting down the propulsion system, the third engineer and a motorman were assigned to troubleshoot a high exhaust temperature issue in the no. 1 auxiliary engine while the vessel was using its no. 2 auxiliary engine to provide electric power for the ship.

The third engineer reported smelling oil and found a small lube oil leak from a crankcase cover door on the running no. 2 auxiliary engine. He went to tighten a bolt, but before he could there was an explosion and fire along with low lube oil pressure and oil filter plugged alarms. Both the engineer's and motorman’s overalls were on fire with the motorman more seriously injured.

NTSB commends the quick response of the crew in sealing the engine room by closing watertight doors, shutting off ventilation fans, closing dampers, and activating quick-closing fuel valves to effectively starve the fire of fuel and oxygen. They prevented the spread of the fire and the fire self self-extinguished. 

The captain saw thick smoke coming from the funnel and immediately returned to the bridge. The passengers were mustered and evacuated without injury. Local fire crews responded but found the situation controlled.

 

Fire damage to the no. 2 auxiliary (NTSB report)

 

The subsequent investigation found that the no. 2 engine was damaged beyond repair. The engine block had cracked, and investigators found a 10-inch high and 16-inch wide hole and reported one of the connecting rods had been ejected. There was damage to the no. 1 auxiliary engine from the fire as well as the turbocharger, piping, cables, and electrical wires and lighting in the engine room. The NTSB reports the cost of the casualty at $2.4 million.

The NTSB investigators concluded that 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 subsequent fire from the ignition of atomize 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 NTSB writes in its report. “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.”

The analysis of the lube oil in the no. 2 engine identified abnormally high levels of aluminum and iron. It had increased significantly since the last in-service sample was taken in September. There was also an increase in lead and tin. 

The vessel was sold during the bankruptcy of American Queen Voyages and Hornblower. The subsequent survey for the repairs showed that the engine block, crankshaft, several main bearings, connecting rod bearings, and the no. 14 fuel injector were all damaged during the explosion and fire with the plunger of the no. 14 fuel injector broken off, pistons and pins and other components from the nos. 13 and 14 cylinders “totally destroyed.” They also observed “heavy local wear” in main bearings and signs of cavitation that were not typical and also suggested oil quality or other lube oil issues.

NTSB concluded that debris in the system would have caused scratching or scoring of the inner layer of the bearings as the debris circulated. The wear would have permitted more lube oil to flow out the sides of the bearings, reducing pressure, and generating excessive heat. The lack of changing out the filter elements made the filter less effective or it could have clogged and a bypass value would have permitted more debris into the system.

These factors they believe contributed to the failures and catastrophic mechanical damage to the engine. The hot oil spewing out started the fire.

Repairs were made to the ship and it returned to service under its new owners in April 2025. The complete report is available online.