Section 05
Troubleshooting
Symptom-first diagnosis: no crank, no start, overheating, smoke, alarms, vibration and emergencies.
36Marine Diesel TroubleshootingDiagnose marine diesel faults systematically: work from symptoms and recent work to measurement, and prove the cause before you buy any parts.37Marine Diesel Will Not CrankDiagnose a boat engine that clicks, cranks slowly or does nothing, working from batteries and connections through to the solenoid and starter.38Marine Diesel Cranks but Will Not StartDiagnose fuel, air, stop-control, glow and compression causes when a boat diesel cranks normally but will not fire, in the order worth checking.39Marine Diesel Starts Then StopsWhy a marine diesel starts and dies, surges or stops under load, and how filter work, refuelling and air leaks cause most of these failures.40Marine Diesel Loss of PowerDiagnose a marine diesel that will not reach rated rpm, slows under load or delivers poor boat speed, and separate engine faults from overload.41Marine Diesel OverheatingDiagnose high coolant temperature, weak raw-water flow, steam and overheating that appears only under load, in the order that finds it fastest.42Marine Diesel Smoke ColoursWhat black, white, blue and grey exhaust smoke mean on a marine diesel, how to tell them apart, and which ones mean stop the engine now.43Marine Engine Alarm TroubleshootingHow to respond safely to oil-pressure, temperature, alternator and exhaust alarms on a marine diesel, and what to check before you restart.44Marine Diesel Vibration and NoiseFind the source of knocking, rattling, squealing, drumming or driveline vibration on a boat, and tell engine noise from propeller and shaft noise.45Gearbox, Saildrive and Propeller TroubleshootingDiagnose no thrust, delayed engagement, slipping, saildrive faults, fouled propellers and shaft vibration without dismantling the gearbox first.46Marine Engine EmergenciesImmediate actions for diesel runaway, engine-room fire, flooding, fuel leaks, loss of cooling and seawater inside an engine.47Diesel Bug, Water and Contaminated FuelHow to identify microbial growth, water and sludge in a boat fuel tank, why repeat filter changes never fix it, and how to remove the source.