⚠️ This article is provided for general information and guidance only. It does not replace the advice of a qualified marine engineer or the instructions in your engine manufacturer’s manual. Always follow the manufacturer’s recommendations and observe proper safety procedures when working on or around your engine. If you are unsure about any condition, fault, or maintenance task, consult a professional marine diesel mechanic.
Do you carry out a simple inspection of your sailboat’s diesel engine before pressing the start button? These three easy steps can add years of life to your boat’s most important workhorse.
Most small-boat diesel mechanics agree that sailboat engines are often more abused than any other type. Many of us only run our engines to leave or enter a marina, usually at low speed and for short periods.
Diesel engines perform best when they are brought up to full operating temperature and occasionally run under proper load. Long periods of light use can lead to carbon build-up, clogged injectors, and other problems. You can greatly extend your engine’s life by following these simple steps:
1. Set up a maintenance schedule
Follow the manufacturer’s recommended preventative maintenance schedule exactly. Your owner’s manual will tell you how often to change oil, filters, impellers, belts, and other key components. Regular servicing is the foundation of a reliable diesel.
2. Hire a good marine diesel mechanic
Once a year, hire a reputable small-engine diesel mechanic for a thorough inspection. Ask them to go over the engine carefully and explain what they find. This is an excellent opportunity to learn more about your engine and catch problems early. Expect to pay around £200–£400 depending on location and scope of work, and consider it money well spent.
3. Use this quick seven-point inspection before every trip
Make these checks each time before you get underway, whether from a dock, mooring, or anchorage. Even if you checked the day before, conditions can change.
• Oil
Use the double-dip method: pull the dipstick, wipe it, reinsert fully, then check again. Diesel oil normally turns black quickly, so colour alone is not a problem. Look for:
Milky or cloudy oil → possible water contamination
Metallic particles → possible internal wear
Strong fuel smell → possible fuel dilution
• Transmission fluid
Check using the double-dip method if your gearbox has a dipstick (some modern systems use sight glasses). Smell the fluid. A burnt odour indicates overheating or wear and needs attention.
• Coolant cap and level
Only check when the engine is cold. Remove the cap, inspect the gasket, and replace the cap if the seal looks worn. Check the coolant level and keep it near the top of the tank. Never remove a cap from a hot engine.
• Belts and hoses
Press belts for tension. More than about ½ inch of play means adjustment or replacement is needed. Feel hoses (cold only) for softness and inspect for cracks or chafe. Carry spare belts and hoses onboard.
• Stuffing box (traditional shaft packing only)
If your boat has a conventional packing gland, check for leaks. Three or four drips per minute are normal when running. More than this indicates adjustment or repacking is needed. Many modern boats use dripless seals, which have different inspection requirements.
• Raw-water seacock and exhaust
Confirm the seacock is open before starting. After start-up, check for a steady flow of cooling water from the exhaust. No water usually means a blocked strainer or intake.
• Battery cables
Vibration can loosen connections. Check that all battery terminals and engine connections are tight and free of corrosion.
These simple checks, combined with regular servicing and proper engine use, will significantly improve reliability and help your diesel engine give many years of dependable service.
⚓ Captain John Jamieson shows small boat cruising skippers how to reach their sailing dreams on his website Skipper Tips.
This article was first published on 7 December 2009