There is a difference between going on a journey in your car and setting out on a boat trip. It is wise to take some time before every journey to do some basic checks on your engine or engines.
Diesel engines are fairly robust these days, and if they have the basic consumables, they will run—even if they are not running very well. Some diesel engines are more complicated than others, so once you have confirmed that you have the basics, you may need to call an engineer if it still is not running correctly.
The first system I check when on board is the raw water system.
Raw water will come from the sea to the through-hull fitting and then a shut-off valve. The inline valve will allow water to pass when the lever is in line with the pipe. It is good practice to exercise the valve whenever you do your engine check. This will ensure that the valve does not seize in the open position and prevent you from closing it when you require it to be shut.
The raw water will then flow up to a strainer, and the strainer’s job is to stop the items from being brought from the sea into the engine. These items could be; weeds, fish, sand, stones…………. anything in the water could be pulled up into the raw water system. Some strainers will allow you to have a visual check to see if anything has been caught, and if the flow is obstructed too much, then your engine lubricants and cooling system will not work properly. The strainer will need to be removed and cleaned out.
The raw water from the strainer will go along a pipe to the raw water pump and the impeller, which will be made of relatively stiff rubber.
The impeller is a serviceable item that needs to be changed at the frequency prescribed by the manufacturer. If the impeller is overused, it could start to break up, and potentially small parts could get lodged further into the raw water system.
While running the engines, monitor the temperatures closely. If they begin to rise and your strainer has a glass top, inspect the strainer to check whether it is clear. Should it appear clear, place your hand on the impeller housing to assess its temperature. A hot impeller housing likely indicates an issue with the impeller. For those with a new boat, it’s wise to practice changing the impellers while docked, with ample time and favourable conditions, rather than facing the challenge at sea with hot engines and cramped working spaces.
The raw water will then go through heat exchanges to cool down (depending on the engine) the coolant, the oil, the gearbox oil, the exhaust manifold, the air intercooler, and finally, the exhaust to cool down the gases that leave the boat. If you have a GRP or wooden boat, this is very important. When you first start your engine, you must ensure that the raw water flows from the exhaust. This will confirm that the raw water system is operational.
The coolant is the liquid that cools the engine. We do not want raw / salt water passing around the engine, as it will erode the metal. For example, in a car, the coolant will have an additive (prescribed by the manufacturer). The additive will stop the engine from getting too hot or freezing when it gets too cold.
Coolant: I usually check the coolant level next. The expansion or header tank may be used to visually check the coolant level. The tank shows the minimum and maximum levels, and the coolant should always be somewhere in between.
Your engine or engines may not have an expansion tank, which means there will be a lid on the top of the heat exchange for the coolant. You can either remove the lid and see into the heat exchange to check the level or possibly dip your finger in to feel the coolant level. This should only be done when the engine is cold.
Coolant from one of the engines may be used to heat the boat’s tap water. The coolant will be sent around the calorifier (boiler). This will enable you to have hot water from the facilities for sinks and showers while underway.
Oil: is the main lubricant for both the engine and the gearbox, with the gearbox requiring a separate, specialised oil as specified by the manufacturer. The levels of engine and gearbox oil are checked using a dipstick.
To check the engine oil, pull out the dipstick, clean it thoroughly, and then reinsert it fully before removing it again to take a reading. The dipstick typically features notches or hatched areas to indicate the correct oil level. Maintaining the proper oil level is crucial, as having too little or too much oil can cause engine issues. When finished, ensure the dipstick is fully reinserted into the engine.
The gearbox oil dipstick will probably be a screw-in plastic fitting. Be careful when screwing this into the gearbox, as the plastic thread on the dipstick is going into a metal thread of the gearbox. You do not want this to be cross-threaded. You will need to take advice from the user manual to see what position the dipstick needs to be in to get the reading.
The belts on the engine need to be in good condition. A healthy black colour with a good tread on them, all the way around. If there is a lot of black dust in the bilge area around the belts, this is usually a sign that the belts are degrading and need changing. The belts also need to be the right tension. A good rule of thumb is twisting the belts to see if they will get to 90 degrees. However, some systems have automatic tensioners; you will need to know the details from the manual.
Bilges will not only show the belts deteriorating but also oil, coolant, and raw water leaks…………. It is best to keep your bilges clean so that you can instantly see if a problem is manifesting. While you are checking the bilges, it is worth checking the bilge pump and the float switch. If you are on a boat for the first time, it’s worth taking a video of the engines and bilges so you have something to refer to later.
Levels: You may have other systems with hydraulic levels that need to be checked, such as your trim tabs and power steering. These levels are worth looking at while in the engine bay/engine room.
Electric wiring and hose clamps can be visibly checked while you are in the engine bay. You do not want any of the wiring or hoses to be chafing while the engines are vibrating under load, and the vibrations could cause hose clamps to become loose.
These checks will only take a few minutes once you are in the habit of doing them, but they are well worth it to protect yourself.
The acronym W.O.B.B.L.E is sometimes used as a reminder of the checks:
Water
Oil
Belts
Bilges
Liquids
Exhaust water flow / Everything else