Marine Diesel Turbocharger Care: Warm-Up, Cool-Down and Simple Checks

Start the engine and let it idle briefly so oil pressure comes up and oil reaches the turbo bearings. Then run at moderate rpm and light load until the engine reaches normal temperature, as your manual describes. Avoid revving a cold engine hard in neutral or pushing straight to full throttle from a cold start.

Turbo diesels do not like endless idling and light loads. A yard manager quoted by Power & Motoryacht says the biggest turbo problem he sees is owners who never use them. When conditions allow, run the engine up to its full rated rpm for a short time each outing. PassageMaker adds that this also tells you whether the engine can still reach its rated rpm; if it cannot, it is overloaded and you should find out why.

After running hard, let the engine idle for about five minutes before switching it off (Power & Motoryacht's guidance; Westerbeke says 5 to 10 minutes at no or light load for turbo generators). A turbo that is still spinning fast loses its oil supply the moment the engine stops, which wears the bearings, and the heat can bake the leftover oil into deposits. A slow run through the no-wake zone and docking time count toward the cool-down. Check your own manual's guidance.

Change the oil and filter on your manual's schedule with oil that meets its diesel specification (see the diesel oil and filters guide). The turbo's bearings run on engine oil, so old, sooty or fuel-diluted oil hits the turbo first. An annual oil analysis can show early wear. Watch for oil leaks at the turbo's oil feed and drain lines.

With the engine off, open the air filter housing and look at the element. A clogged filter starves the engine of air. BoatUS warns it causes black smoke, overheating and power loss, and on a turbo engine can damage the oil seals. Clean or replace it as your manual says, at least once a year. Make sure nothing (rags, tools, bits of filter) is left in the intake.

If your engine has a boost gauge or shows boost on its display, write down boost at several rpm settings when the boat is clean and running well, along with the sea state. A Yanmar technical specialist told Power & Motoryacht that boost is the best tool for judging a turbo, and that a drop of about 10 percent from your normal reading (with a clean bottom and clean filters) means the turbo needs cleaning. Black smoke alone can also come from a dirty air filter, so boost readings are more useful.

With the engine off, look all around the turbo and its hoses for:

• oil on the outside of the turbo or inside the intake hose
• water dripping onto the turbo, or rust and salt crust on it
• soot around flanges (an exhaust leak)
• a rusty wastegate actuator rod

Power & Motoryacht describes a "failed" turbo that was really a wastegate rod rusted by saltwater dripping on it. Find and fix the drip, usually a raw-water hose or fitting above. Lift the insulation blanket where you can to check underneath, and replace a blanket that is oily, torn or cracked.

With the air filter or intake hose off, shine a light at the compressor wheel. Its blades should be clean and sharp right to the tips. Rolled, nicked or bent blades mean something got in and the turbo needs a professional; don't just wash it. Oil inside the compressor housing or intake also needs a mechanic. BoatUS adds that, with the engine off, a turbo that has play or does not turn easily needs replacing; if you check this, touch only the center nut gently, never the fragile blades. Never put anything near the wheel with the engine running.

Some makers, Yanmar among them, specify a turbo wash: a water-based cleaner sprayed slowly into the air intake in small bursts with the engine running at the rpm the manual specifies, usually in neutral. It cleans soot from the compressor, intake and turbine. Use only the cleaner and method your manual names, go slowly, and never pour a large amount in at once. If you are not comfortable doing it, let your mechanic do it at the next service.

When the exhaust elbow or mixing elbow is off for inspection, look into the turbine outlet. A light coat of fine ash is normal; Power & Motoryacht suggests removing it with a vacuum without touching the blades. Oily clumps, rust or moisture mean raw water or oil is getting where it shouldn't, and the turbine blades should not be damaged or rubbing. Check the elbow itself for rust and clogging at the same time (see the exhaust elbow guide).

Keep the engine room dry and clean so drips are easy to spot. Fix raw-water leaks right away, keep hatches and vents from letting spray land on the engine, and touch up rust before it spreads. The late Richard Thiel, a former diesel mechanic writing in Power & Motoryacht, noted that big diesels can draw salt spray in with their combustion air; if you regularly find a film of fine salt on the engine, ask a mechanic about intake baffles or demisters for the engine-room vents. He also points out that hot engine-room air holds less oxygen, so blocked or undersized vents cost power, and any changes to engine-room ventilation should follow the engine maker's air requirements. Water in the exhaust can also come from backflow, so follow good shutdown habits and keep the exhaust system in good shape.

Record boost readings, filter changes, cleanings and anything you saw in BoatMend. Comparing year to year is how you catch a slowly failing turbo early.