TBO (time between overhauls)

Time between overhauls, TBO, is the running-hours interval the engine maker sets between scheduled strip-down overhauls of major components: piston and rings, cylinder liner, bearings, fuel injection equipment, and turbocharger. Values vary by component and engine: large two-stroke piston overhauls and bearing inspections run into tens of thousands of hours, while injectors and exhaust valves come out far sooner. Fuel quality, load profile, cylinder-oil feed, and water in the lube oil all shorten it. Condition monitoring, liner-wear measurement, scrape-down oil analysis, and bearing-temperature trends let operators move from fixed-hour overhaul to condition-based intervals, extending TBO where the data supports it.