Top tips to help keep you going.
Modern marine diesel engines are pretty reliable things - most of the time. Feed them with diesel and air, cool them with seawater/coolant and add sufficient lubricant to keep the cogs turning and they will often give hundreds or thousands of trouble free hours.
However we all have our off-days and diesel engines are no exception. Knowing a few troubleshooting tips will go a long way to keeping you going.
When checking the engine, isolate the engine battery and remove the engine keys, so that others cannot start the engine whilst you have hands in the way. Consider using plastic/latex gloves.
Be fastidious about keeping the engine compartment clean. It makes spotting a potential leak or problem so much easier.
The crankshaft, usually the pulley wheel at the bottom of the engine, usually drives the belts. Belts transfer power to other pulley wheels on the engine and drive the alternator, to provide power to the batteries, and the water pump to circulate cooling water around the engine.
If the belt is too loose:
A slipping or loose belt is often visually indicated by black belt dust around the engine near the pulleys. There are two common types of belt; flat belts or ‘V’ shaped. Consult your owner’s manual about their accurate testing and adjustment, but a common rule of thumb to check adjustment is:
A belt adjusted too tight can put excess pressure on the pulley wheel shaft and increase wear on the shaft bearings of the pulley wheels.
A properly functioning engine does not really consume much lubricating oil; it just uses the oil to lubricate and cool its moving internal parts. So if the correct level is checked it should stay roughly the same and only change over longer periods, unless there is a problem. Oil is kept inside the engine and separate from the water and fuel system by internal seals and gaskets.
The ways that oil escapes from the engine is by leaking through an engine seal or gasket. There are three visual ways to check for oil leaks:
1) Externally looking for leaks around the engine and engine tray
2) Oil leaking through a seal and mixing with the water cooling system.
3) Oil leaking into the combustion chamber, through the piston rings and coming.
The oil will burn in the combustion chamber and change to blue smoke coming out of the exhaust.
Oil levels need monitoring and too much or too little oil is bad for the engine. Looking at the condition of the oil is a little like reading tealeaves.
Many modern marine diesel engines have both seawater cooling and fresh water cooling. The seawater cools the fresh water/coolant that circulates around the engine.
Checking the seawater intake strainer is the main check on the seawater system apart from running the engine and ensuring that seawater is exiting through the exhaust (if you can see it). The exiting seawater water also quietens and cools the exhaust so if water is not passing through the exhaust, the exhaust note sounds hollow.
Times when seawater circulation can be a problem are:
A way of establishing whether the seawater or freshwater system is the problem when the overheat alarm sounds, is to:
Want to know more about diesel engines, then check out the RYA DieselEngine Handbook, written and illustrated by Andrew Simpson, availablefrom the RYA Shop
Buy RYA Diesel Engine Handbook at the RYA Shop
Buy RYA Diesel Engine Handbook (eBook) at the RYA Shop