How To Extend The Service Life Of Marine Engines?（1）

We usually see engine service time as an important comparison parameter in second-hand ship transactions. Some people may also ask how long a ship’s engine should work. You will hear a lot of answers to this question, but in fact there is no standard answer. The life of an engine depends on many variables, so no one can accurately predict the life of an engine. But we can talk about some things about engine life.

First, diesel engines generally have a longer life than gasoline engines. There are two main reasons for this. First, at a given ship speed, they make fewer turns, usually about one-third less than gasoline engines. When the engine speed per kilometer decreases, the stroke of the piston up and down the cylinder will decrease, and the opening and closing of the valve will also decrease. Therefore, the corresponding wear is also reduced.

Another reason is that diesel has viscosity, so it not only provides combustion fuel, but also has a lubricating effect, while gasoline is pure fuel. In addition, we all know that a diesel engine consumes less fuel per unit of driving than a gasoline engine, and the most reliable indicator of engine life is the amount of fuel it burns. Keep this in mind, and I will talk about it later.

Let's talk about what happens to an old engine. Some of these devices work for a long time, so that the piston ring and/or valve guide are worn out, so that the lubricating oil enters the combustion chamber through the piston ring and/or valve, and burns with the fuel. The result is a cloud of blue smoke, but the engine is still running, and usually runs surprisingly well. However, fuel consumption will only get worse, and it is inevitable that there will be such problems: either it is too troublesome to bear, or the spark plug starts to be contaminated with oil residue, the engine starts to fail, and eventually it cannot start.

This is a manual oil pump that draws oil from the bottom of the engine to achieve a complete oil change. There is another kind of wear, that is, the core of the engine (pistons, crankshafts, bearings, valves, etc.) is in good condition, but the auxiliary accessories start to fail due to various reasons, which is usually related to corrosion. The auxiliary accessories mentioned here refer to the water pump, carburetor/fuel injection system, exhaust pipe elbow and ignition parts. This situation usually does not cause too many problems, but will cause start-up difficulties, poor performance and high maintenance costs.

How to solve the above problems? We all know that the best way to prevent engine wear is to change the lubricating oil at regular intervals, but what is an "appropriate interval"? Start with the recommendation of the engine manufacturer, which is applicable to the engine in normal use; that is, it is not applicable to problems such as abnormally heavy load, high temperature, or exhaust fouling. Assuming your engine does not fall into this category, there is absolutely no benefit in changing the oil more frequently. The efficacy of modern lubricants, even the cheapest API-grade lubricants, is of no avail if replaced within the prescribed time; doing so will not prolong the service life of the engine. You will only waste money, but also need to deal with the waste generated.

This is a component that needs to be replaced. In theory, it is possible to let your engine undergo such violent operation that you need to reduce the oil change interval, but it is unlikely. The most likely cause of "serious operation" of ships is long-term low-speed operation, incomplete fuel combustion, and severe overload. Due to electronic control, the former is unlikely to be a problem with modern engines, while the latter is even rarer, unless your operating time or mileage has exceeded twice the theoretical data. In other words, most of us should follow the factory’s recommendations.

Some ships may encounter low-quality fuels that contain high concentrations of sulfur. Sulfur is converted into extremely corrosive sulfuric acid during combustion and accumulates in the lubricating oil. The machine does not filter it, and the only way to eliminate and prevent it from corroding bearings and other soft metal parts is to change the oil. So pay attention to the sulfur content in the fuel (there is an inexpensive test tool to detect the sulfur content).

It is best to remove the hose from the exhaust elbow every year to check for corrosion. What about synthetic motor oil? Will it increase the life of the engine? Compared with petroleum, the wear rate of synthetic materials is lower, and how much the specific changes are, whether this means a longer engine life is debatable. From a personal point of view, any good api grade lubricant can almost achieve the same effect, while the cost is only a small part.

The last note about engine oil is: if you want your engine to be durable, make sure whoever changes it must do it in the correct way. For most ships, the maintenance recommendations of the engine manufacturer (by the way, whether you use mineral oil or synthetic oil) mean changing the oil once a year. If your boat stays in a cold place in winter, change the oil as close to winter as possible to prevent damage caused by the natural accumulation of winter pollutants in the engine. Ideally, the oil should be drained before the tug, and then refueled, and then run the engine for a minute or two to ensure that all parts are covered with clean oil.

When you start the boat in the spring, remember that all the oil has settled in the sump of the oil tank, let the engine idle for one to two minutes, and let everything recirculate. If you don't do this, the amount of wear you produce in five minutes is equivalent to the amount of wear in the rest of the year.