Your engine is your safety net when the wind dies or the manoeuvring gets tight. Here’s my 100-hour service checklist for a Volvo Penta D2-40 (but most of it applies to any marine diesel):
Every 100 hours (or annually, whichever comes first):
- Change engine oil and filter
- Change fuel filter (primary and secondary)
- Check/replace impeller — don’t wait for it to fail
- Check belt tension and condition
- Check coolant level and antifreeze strength
- Clean raw water strainer
- Check anodes (heat exchanger and elsewhere)
- Check alternator output
- Inspect exhaust elbow for carbon buildup
Every 200 hours:
- Change gearbox oil
- Check prop shaft seal/cutless bearing
- Service fuel injection system (professional job)
Daily checks (before every trip):
- Engine oil level
- Coolant level
- Belt condition (quick visual)
- Raw water strainer (clear?)
- Exhaust (check water is coming out with the exhaust)
The most neglected item on this list? The impeller. A failed impeller means no cooling water, which means an overheated engine, which can mean a catastrophic head gasket failure at sea. Carry a spare and change it before it disintegrates.
What does your maintenance routine look like?
Good list James. I’d add: change the impeller at the start of every season regardless of hours. The rubber deteriorates even when it’s not running, especially in the Med heat. A €15 impeller is a lot cheaper than a new heat exchanger.
I also bleed my fuel system at every filter change. Air in the fuel lines is the most common reason for a diesel engine not starting, and it always happens at the worst possible moment.
I’d add zinc anodes to the must-check list. In Mediterranean waters they corrode fast — I check mine monthly and replace them every 3-4 months. The salt content and water temperature here eat them much faster than in northern waters.
Also, a tip: keep a maintenance log with dates and hours. It’s not just good practice — it adds value when you sell the boat. A buyer who sees a complete service history pays more.
On the charter boats we service at 250 hours or every 6 months, and the number one failure we see is fuel contamination. Med marinas can have dirty fuel and the warm temperatures promote diesel bug growth. I’d add: use a fuel biocide additive at every fill, and drain the water trap on your primary filter regularly.
Also, RUN your engine regularly even if you’re at anchor. A diesel that sits for weeks without running develops problems.
Bookmarking this for when we have a boat. I’ve got a background in mechanical engineering so I’m looking forward to doing my own maintenance. Is there a good marine diesel course anywhere in Mallorca? I’d like to learn the specifics before we buy.