- Service once a year or at the hours the manufacturer specifies, whichever comes first.
- The raw water impeller is the most common cause of overheating.
- Fuel filters and water separators matter more in hot climates with condensation.
- Keep a record of every service; it adds value when you sell.
How often?
Manufacturers specify service intervals in running hours and in time. Leisure boats rarely reach the hours, so the annual interval is usually what applies. Oil, filters and rubber parts age even when the engine is not used.
Inboard diesel: typical annual service
- Engine oil and oil filter change.
- Fuel filters and water separator; drain and inspect for water and diesel bug.
- Raw water impeller replacement and strainer clean.
- Check of belts, hoses and hose clamps.
- Coolant level and condition; heat exchanger inspection where accessible.
- Engine anodes (zincs) where fitted.
- Air filter, engine mounts, exhaust elbow and mixing elbow condition.
- Gearbox oil, shaft seal or saildrive seal and saildrive oil.
- Test run with checks for leaks, temperature and charging.
Outboards
For outboards the list is shorter but just as important: gear oil change (look for water in the oil), impeller and water pump inspection, spark plugs on petrol engines, fuel filter, anodes, propeller and shaft grease, and a check of steering and throttle cables.
Sterndrives
Sterndrives add bellows, gimbal bearing, drive oil and alignment to the list. A torn bellows can let water into the boat, so they are worth replacing on schedule rather than waiting for a failure.
Ask your mechanic to keep the old impeller and send a photo. Missing or cracked vanes mean pieces may be stuck in the cooling system and should be found.
Warning signs between services
- Little or no water from the exhaust outlet of an inboard, or a weak telltale on an outboard.
- Temperature rising at cruising speed.
- White, blue or black smoke that is new.
- Hard starting, vibration or a change in sound.
- Diesel, oil or coolant in the bilge.
Why heat matters in Spain
High summer sea and air temperatures reduce cooling margin, and the boats are used intensively in a short season. A cooling system that coped in spring may not cope in August. That is why a pre-season service is more valuable than one in the middle of summer.
Krautic arranges engine services with vetted marine mechanics at your marina, with a fixed price agreed in writing and a short report of parts changed and anything that needs watching.