With half the annual 3500 RNLI call outs to leisure craft being engine related, engine maintenance is of major importance.
Most routine maintenance can be undertaken by the boat owner, but even if you use professional help, a good understanding of what's required can go a long way in preventing engine problems.
DAILY CHECKS
There really is no excuse for not carrying out some basic daily checks. A case in point is a club yacht in daily use that had water in the oil sump (how that happened is another story for another day) that was not detected for 2 weeks. This resulted in a £2500 engine rebuild that could have been prevented had a daily check of the oil dipstick been made!
- Engine oil level
- Coolant level (freshwater cooled engines)
- Drive belt tension
- Seawater pump tell tale drip hole (check for dampness, which indicates a failing water seal)
- Primary fuel filter water separator bowl (much easier if the bowl is transparent and the filter is accessible)
- Cooling water sea-cock is open (if you are in the habit of closing it)
- Operate stern gland lubricating dispenser if fitted
WEEKLY CHECKS
- Oil dipstick ( you are checking for any change in colour rather than quantity)
- Cooling water filter (if there's lots of floating weed around, this will become a daily check)
ROUTINE MAINTENANCE - (see engine handbook)
Lubrication
A diesel engine needs to be worked hard and should never be stopped until it has attained working temperature. An engine that runs too cool will experience internal condensation and a by-product of combustion will be sulphuric acid.
Engine oil contains additives that combat corrosion and these are depleted whilst doing their job. It's therefore essential that the engine oil is changed at least as often as the handbook specifies, and on most leisure yachts, that's going to be an annual job, despite having less than the specified number of hours. The oil filter should be changed at the same time.
Ideally this will be done in the Autumn, so that fresh oil remains in the sump over the period when the engine will not be used.
Remember that gearbox oil needs to be changed at the specified intervals and this oil may be the same or a different specification from the engine.
Cooling system
The coolant in a freshwater cooled engine should be changed every second year, as, just like the engine oil, the antifreeze (summer coolant) contains corrosion inhibitors. Failure to do this will eventually lead to cylinder head gasket failure.
Seawater cooled engines (direct cooling) should have the water system drained if the boat is to be laid-up to prevent frost damage.
Ideally they should be flushed through with freshwater and then be filled with a 50/50 mixture of freshwater and anti-freeze, because if left drained corrosion will occur. This is achieved by running the engine supplied from a bucket of freshwater with antifreeze added as the bucket reaches a quarter full. The thermostat must be open before you do this.
If there are sacrificial anodes in the cooling system, these must be checked annually and replaced if more than half used.
Replace the water pump impeller annually and check the condition of the water pump drive belt if fitted.
If you have a syphon-break that contains an air valve this needs to be serviced annually because a sticking valve will cause water to enter the working parts of the engine, and there is no indication of the correct functioning of the valve.
Fuel system
The fuel system should have two filters, a water-separating primary filter and the engine fine filter. The transparent bowl of the water-separating filter will give a good indication if there's any dirt or water in the fuel tank. If there is, this should be tackled, a task that's very difficult on the majority of modern yachts. Although the primary filter is not covered by the engine service schedule, it's sensible to change it when you change the engine filter. After changing the filters, the fuel system will require 'bleeding'. This is not a difficult job, so have a go yourself, so you know how to do it at sea, should you ever need to. Paint the 'bleeding points' for easy recognition.
Annual service of the fuel injectors is not likely to be required, and in general, if there are no symptoms, leave them alone.
Air system
Change or clean the air intake filter annually as required. Carefully check the condition of the water injection bend of the exhaust system, as this can corrode and then deteriorate rapidly allowing water and exhaust gasses into the boat.
Electrical system
Check and clean all terminals/connections annually. Ensure the battery is clean and dry and the terminals clean, tight and greased with 'Vaseline' (petroleum jelly). If the boat is to be laid up, slacken the drive belt, but re-tighten it before use. Ensure the battery is charged monthly during any period of lay-up.
