How Does A Marine Diesel Engine Work?

Instead of utilizing a spark to ignite gasoline, a diesel engine builds up enough pressure in its cylinders to heat the fuel to the point of ignition, with the atomized diesel fuel pumped straight into each cylinder at the precise moment.

What is the operating principle of a marine diesel engine?

The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which the fuel is ignited by the raised temperature of the air in the cylinder as a result of mechanical compression; it is thus a compression-ignition engine.

What is the difference between a marine diesel engine and a regular diesel engine?

There is no one-size-fits-all diesel engine for all applications. Industrial uses, for example, truck applications, electrical power production, RV applications, heavy duty emergencies, pumps, and, of course, marine applications are all available. Despite the fact that each engine is slightly different, the basic concept remains the same. Marine engines have distinct exhaust, cooling, electrical, and fuel systems. The differences between industrial diesel engines and their marine counterparts will be discussed in this article.

For a variety of reasons, diesel engines are popular among mariners. Unlike gas marine engines, there aren’t many manufacturers of just diesel marine engines on the market. Industrial diesel engines are built by huge corporations like Caterpillar, Cummins, and Detroit Diesel, and then adapted for the heavy-duty marine industry. The marine engine is based on the design of millions of other truck or off-road engines now on the market. As a result, Volvo, Yanmar, and Perkins all provide engines for smaller pleasure craft that operate well as drop-in replacements but not for bigger vessels.

Marine vs. Industrial Usage Profile:

Industrial engines, it is a popular myth, will not work in marine applications. Marine diesel engines can be converted from industrial diesel engines. The majority of pleasure craft only get 100-300 hours of use each year. The average time between overhauls for heavy-duty marine applications is 10,000-15,000 hours. Regardless of application, all marine engines have a shorter projected duty cycle than their industrial counterparts, which can routinely travel 500,000–1,000,000 miles before requiring major maintenance. The reduced lifespan is due to the fact that pleasure craft marine engines operate at consistent high speeds and lower RPMs for a limited time. When you think about it, speed boats are only used for sailing canals and the open ocean.

The utilization profile of heavy duty marine applications is similar to that of pleasure ships, except that they operate at full speed for substantially longer periods of time. There are no stoplights or speed limits on the open water. Industrial and vehicle engines typically run at lower rates and only increase RPMs when the transmission shifts 5-6 gears briefly. Only one gear is used by marine engines. A widespread misunderstanding is that a marine engine with less hours is better than one with more. Corrosion and lack of lubrication are common problems with idle marine engines. Truck and industrial diesel engines will frequently last far longer than their marine counterparts due to their constant use.

The engineering differences between industrial and marine engines are driven by this utilization profile. The risk of fire and corrosion are the two main reasons why marine engines are built differently than industrial engines. Marine engines are subjected to a constant onslaught of moisture and water exposure. If not mitigated, this exposure to water (typically salt water) may swiftly damage cast iron and steel. Industrial engines are often used in dry locations, are stored out of the elements, and are not subject to fuel leakage on ancillary components or on the road.

Main Differences Between Marine and Industrial Engines:

Starter – Instead of normal paint or a bare casting for an industrial diesel application, the starter on a marine application is covered in epoxy. Epoxy is a rust-prevention coating that can be applied on aluminum, industrial cast iron, or steel. To keep water out of a marine starter, some points are sealed. A marine starter’s casings are spot welded for increased strength to prevent them from cracking. A gasoline-powered automobile or industrial engine can split and enable sparks to enter the engine bilge.

Alternator — A marine-rated alternator has an extra plate behind the fan near the screen. On the back, there is an additional spark arrestor screen. A spark is prevented from entering the bilge by these plates. Engine fires at sea are no laughing matter, and every precaution must be taken to avoid them.

Distributors — The distributor and distributor cap on gasoline-powered marine engines are prone to corrosion and fire. The distributor’s job is to direct secondary high voltage current to the spark plug, allowing it to fire in the proper sequence. This piece of equipment can be a major fire hazard and needs to be upgraded for marine use. Due to the higher risk of a spark, automotive distributors have an automatic vacuum advance, whereas marine distributors do not. Internal components are stressed by a pressured vacuum, which raises the risk of structural failure. Internal operational agreements vary across marine wholesalers. To maintain higher steady RPMs, the springs are thicker. In comparison to an automobile or industrial distributor, the points do not float in maritime distributors. In marine applications, the spark arrestor vent and distributor caps are also different. To avoid corrosion, they are frequently made of brass. The vent, caps, and terminals are all constructed of aluminum in automobile applications. The brass terminals are actually far superior electrical conductors and can withstand the humid atmosphere considerably better. Look for electrical components with the SAEJ1171 international grade, which indicates that the part is suitable for maritime use.

Carburetor – A carburetor is not used in diesel engines. A carburetor is a mechanism that combines the mixture of air and fuel. All diesel engines are fuel injected and designed for compression ignition. Carburetor-equipped automotive gasoline marine engines have a reinforced body to avoid fires. To begin, there is an overflow dam in marine-rated carburetors to prevent fuel spilling. Second, there is a reinforced cover over the carburetor and intake manifold to avoid fuel flooding difficulties. If the fuel in this chamber floods, it will be contained and returned to the carburetor. There is also an additional bracket to keep the fuel line connected to the carburetor securely. The throttle changes are grooved to prevent fuel from leaking out. Fuel will constantly flow towards the blades thanks to the grooved lines.

Fuel Pump – A dual diaphragm fuel pump is used in marine applications. A single diaphragm fuel pump is used in automotive and industrial diesel applications. The dual design serves as a fail-safe in the event that one of the compartments ruptures. If that component fails, especially on gasoline engines, fuel will spill all over the bilge. If that diaphragm fails in an automotive application, fuel will pour all over the place. If the diaphragm ruptures, a high-performance marine fuel pump will also have a bleed-off line. The bleed off-line will return fuel to the carburetor rather than the bilge.

Marine water pumps differ from automobile or industrial water pumps in several ways. Some water pumps are open systems that cool the engine with raw seawater. Because aluminum rusts, marine water pumps come with stamped stainless steel brackets. Stainless steel or epoxy make up the majority of the body. The majority of automobile water pumps are unpainted and prone to rust. The water pump’s interior components are made entirely of brass or anodized aluminum. An electrochemical technique that turns a metal surface to a corrosion-resistant anodic oxide finish is known as anodizing. A stamped steel impeller will be used in automotive or industrial engines. A brass bi-directional impeller in a marine water pump eliminates the need for anti-freeze.

Secondary Differences between Marine and Industrial Engines:

Camshafts – The grinds on marine and industrial camshafts are different. The grinds on RVs and on-road trucks are very identical, but marine engines have overlapping intake and exhaust valves. The camshafts are typically ground with a high lift and short duration for better low-end torque at high RPMs, rather than horsepower, as is the case with many performance camshafts.

Freeze Plugs – To prevent corrosion, all core plugs in marine engines are composed of brass. Corrosion-resistant material should also be used to coat coolant channels.

Gaskets and Housings – Composite plastics are used to make gaskets. To prevent corrosion, head gaskets are constructed of stainless steel.

Dual planes, ceramic rollers, and seals are used to make the intake manifold.

Bearings – Bearings in marine engines are typically larger to accommodate consistent RPMs. The larger size makes it easier to stand up to wear. Bearings are also constructed of stainless steel and are resistant to corrosion.

Pistons – In marine engines, pistons are frequently designed for increased compression. The dish-style heads aren’t required. Older marine engines must still include exhaust gas recirculation (EGR), diesel particulate filters (DPF), catalytic converters, and diesel exhaust fluid to comply with EPA Tier Ratings (DEF).

Rings – The rings on marine engines must be designed to withstand damp conditions. Stainless steel or chrome molybdenum are used to make the rings.

Engine Blocks – Engine blocks are similar in both industrial and marine applications. On the automotive side, it’s been said that GM sells roughly 15% of their engine blocks to Mercruiser directly. There isn’t much of a distinction between the blocks. In terms of corrosion technology, there isn’t much of a necessity if the engine blocks are employed in freshwater applications. Copper or brass are occasionally used in the construction of sumps, but this is not the norm. To avoid moisture, marine-rated blocks are sometimes completely covered with anti-corrosion spray. When the block breaks down, it becomes a powder or shale that may be easily ejected through the cooling system. Breakdowns in automotive and industrial engines can clog oil and water passageways. For heavy-duty marine applications, some engine blocks are rated to endure higher sustained RPMs than their industrial counterparts. To prevent corrosion, certain marine-rated blocks are occasionally cast with additional nickel.

Overall, marine engines have a different torque curve than truck engines. Marine diesel engines operate at 4,500–5,000 RPMs for long periods of time. Truck engines can only maintain high RPMs for a limited time before switching to a lower gear. The added heat and pressure of sustained RPMs will be used to make marine-rated engine blocks.

Every portion of the engine, including the cylinder head, rods, and crankshaft, can be made marine-rated. Performance cylinder heads, connecting rods, and even marine-rated crankshafts will be sold by aftermarket businesses. However, for the majority of drop-in diesel engines, marine-rated heads, connecting rods, and crankshafts are not required.

From a design standpoint, marine and industrial strength diesel engines are very similar. It all comes down to the different ancillary pieces that are designed to prevent corrosion or fire. It’s usually a good idea to consult a marine mechanic to ensure that an industrial diesel engine will fit your needs. It’s critical to check the engine serial number before you buy to ensure you get the right engine for your needs.

How does a marine engine work?

The propulsion of a ship from one port to another is accomplished by marine engines. A marine engine, either 4-stroke or 2-stroke, is mounted onboard ship for propulsion, whether it’s a little ship patrolling coastal areas or a big one voyaging international waterways.

Marine engines are heat engines that convert heat created by the combustion of fuel into usable work, i.e. creating thermal energy and converting it to mechanical energy. Internal combustion engines (a type) are employed onboard ships; the combustion of fuel takes place inside the engine cylinder, and heat is generated after the combustion process.

Ship Engine Working Principle

Internal combustion (IC) engines, as previously stated, are mostly employed for marine propulsion and power generation. The following process can be used to demonstrate how a marine engine works:

– A piston compresses a mixture of gasoline and air inside the engine cylinder, resulting in an explosion of the mixture when pressurized owing to compression. As a result, heat is produced, causing the burning gas’s pressure to rise.

What should you always check before starting a diesel engine?

The starting method for marine engines aboard ships necessitates the consideration of numerous factors. While it is critical that none of these elements be overlooked, there are a few critical steps that must be followed without fail while starting these ship engines.

1. Pre-lubrication of the main engine: Before starting the marine engine, begin pre-lubrication of the main engine. The main engine should be started at least 15 minutes ahead of time, and the auxiliary 4-stroke engines should be started at least 1 hour ahead of time.

2. Check Lube Oil Levels and Other Running Pump Parameters: After starting the lubrication pump, check lube oil levels as well as all other running pump parameters such as cooling water pressure, fuel oil temp and pressure, control and starting air pressure, and so on to ensure that everything is within the acceptable range.

3. Blow Through the Indicator Cocks

How does a marine engine start?

The line diagram for the main engine air starting system is shown in the video, which includes an air bottle to give 30 starting air, a pilot valve to begin the operation, a turning gear interlock, an automatic air start valve, an air distributor, and a cylinder head starting air valve.

The primary air bottle valve is opened to give air delivery. When the valve is opened, air passes through the pilot valve and acts on top of the automatic start valve, causing it to close positively. The other branch provides air until the turning gear interlock, which prevents the air from traveling any farther.

The first turning gear must be withdrawn in order to start the main engine. The interlock will be deactivated, and air will be provided to the automatic start air valve.

The air will not pass through the automated start valve until the start order is provided, due to the spring pressure and further positive closing by the air supplied pilot valve.

The pilot valve shifts and blocks the air on top of the automated valve when the air start lever is pressed in the ECR. The line is vented, and there is no longer any positive closing.

The spring is pushed by air passing through the turning gear interlock, which opens the valve and closes the vent.

The air is now available in the distributor and the cylinder head starting air valve manifold. A negative type cam is used in the distributor for positive overlap.

When air compresses the spring on the concerned unit number 4 distributor valve, the valve is opened to operate the same unit number 4 cylinder head beginning air valve.

The cylinder head beginning air valve closes as the camshaft rotates, venting unit number 4 line. The first unit’s valve will now come into contact with the cam profile, and air will be injected into this unit.

How do diesel engines ignite?

Because both diesel and gasoline vehicles employ internal combustion engines, they are similar. Diesel engines, unlike most gasoline cars, employ a compression-ignited injection system rather than a spark-ignited one. The diesel fuel is pumped into the combustion chamber of the engine and ignited by the high temperatures achieved when the gas is squeezed by the engine piston in a compression-ignited system. Many diesel engines feature additional aftertreatment components that minimize particulate matter and break down hazardous nitrogen oxide (NOx) emissions into harmless nitrogen and water, unlike gasoline vehicles. Diesel is a common transportation fuel, and various other fuel alternatives have engine systems and components that are similar to diesel. Learn about many types of alternative fuels.

Why marine engines have 2stroke?

When a ship is being built in a shipyard, the primary propulsion equipment is the most significant machinery to choose.

Both 2 stroke and 4 stroke engines are widely available on the market, however a 2 stroke engine is more typically utilized as the main engine aboard a large ocean-going commerce vessel and has a significantly larger market.

Despite the numerous advantages that a four-stroke engine provides, such as the small size of the plant, considerably higher RPM or speed, and so on, a two-stroke engine outperforms with a few but critical advantages.

Some of the key reasons why 2 stroke engines outnumber 4 stroke engines as the primary propulsion engines on ships

  • Fuel selection: Fuel prices have skyrocketed, and higher-grade fuel adds to vessel running costs. A two-stroke engine may burn low-grade fuel oil, lowering the ship’s operating costs.
  • The thermal and engine efficiency of a two-stroke engine is significantly higher than that of a four-stroke engine.
  • Power: The majority of two-stroke engines are now large-stroke engines with increased power. As a result, they have a higher power-to-weight ratio than 4 stroke engines.
  • More Cargo: Due to the excellent power to weight ratio of 2 stroke engines, ships can carry more weight and thus more cargo.
  • Two stroke engines are more reliable than four stroke engines in terms of operation.
  • Less Maintenance: A two-stroke engine requires far less maintenance than a four-stroke engine.
  • Direct starting and reversing are more easier with a two-stroke engine.
  • No reduction attachments: Because two-stroke engines are low-speed, no reduction gear or speed reduction arrangement is necessary, as is the case with high-speed four-stroke engines.

However, a two-stroke engine is less maneuverable than a four-stroke engine, and the initial cost of installation of a two-stroke propulsion plant is also substantially more than the cost of running and maintaining a four-stroke engine.

In a two-stroke engine, the money saved on high-grade gasoline can offset all other drawbacks while also lowering the ship’s overall running costs.

What can go wrong with a diesel engine?

Diesel engines are more efficient nowadays, and they emit less black exhaust into the atmosphere than in the past. If your car or truck emits an excessive amount of black exhaust into the air, your air and fuel mixture is probably out of balance. To start and run, both diesel and gasoline engines require a mixture of air and fuel. You’ll notice blacker-than-normal exhaust if the balance is off, which is usually due to a lack of fuel.

Why is marine diesel red?

A guy with a past conviction for an IRA attack on police was found guilty of fuel laundering in Belfast, Northern Ireland. Two tankers, 20,000 liters of laundered fuel, and 140 bags of bleaching powder were seized by customs inspectors.

Fuel laundering is a serious problem in Dublin, according to news sources, and the state loses a significant amount of money in taxes as a result. According to an independent analysis, the Irish Exchequer lost 239 million euro last year due to unlawful money laundering.

What exactly is going on in the Emerald Isle? Fuel laundering by organized crime is being forcefully combated by the Republic of Ireland’s authorities, according to sources. “Gas oil is labelled with fuel colours and additives to separate it from road diesel,” officials said. The procedure of removing the identifiers from fuel is known as fuel washing. It can be sold as road diesel once the marking is removed, taking advantage of the higher prices that occur.”

A colorful dye is added to diesel fuel in several nations across the world. Typically, colored diesel is either tax-free or has a lower tax rate than un-dyed, “clear” diesel. The additional dye distinguishes the fuel’s intended usage for taxation and gives government officials a visual clue if the fuel is being used for something other than its original purpose. And, as the United Kingdom and Ireland have discovered, removing the colour may be a lucrative business.

“Since its inception in 1932, the role of the motor fuels excise tax has evolved. Initially, the tax was one of numerous measures for reducing the deficit. Over the next two decades, rises in the “gas tax” were combined with other excise tax hikes to support emergency spending during warfare. The newly formed Highway Trust Fund received federal fuel (and diesel) tax receipts in 1956.”

This fund is used to build roads and other types of surface transportation projects. From the standpoint of diesel fuel, it seems obvious that vehicles that use the nation’s highway infrastructure, such as trucks and buses, should contribute to its upkeep. Farm tractors, heavy construction equipment, emergency electricity generators, and boats are examples of non-highway diesel users who should not be forced to pay federal excise taxes to fund roadway improvements.

The Internal Revenue Service began looking into ways to make diesel fuel excise tax collection easier in the early 1990s. At the same time, the Environmental Protection Agency required that certain fuel be dyed blue. The dye was designed to identify diesel that did not meet EPA sulfur regulations for use in highway vehicles.

The IRS mandated that all tax-exempt diesel fuel be coloured red, and the EPA’s blue dye was phased out. All diesel used in the United States for “off-road” applications, such as marine, is currently coloured red.

The federal excise tax on highway diesel fuel is 24 cents per gallon this year. Diesel gasoline without color is likewise taxed at 32 cents per gallon in Florida. That implies red-dyed, off-road diesel used on a boat in Florida should cost around 56 cents per gallon less than clean diesel.

A bulk delivery of 5,000 gallons of fuel to a boat by tanker truck or fuel barge in Ft. Lauderdale comes to $1.80 per gallon. If a captain could drive the yacht along US Highway 1 and pull into the cheapest petrol station, on-the-road fuel would cost $2.50 per gallon.

As a result, red fuel is 70 cents cheaper than clear diesel, with the tax exemption accounting for 56 cents of the difference. The remaining 14 cents are used to support the gas station’s infrastructure expenditures.

Similarly, higher marina fuel costs are warranted to cover the expense of the fuel distribution infrastructure required for selling fuel on a body of water. To avoid leaking pipes and fittings, which could result in a gasoline spill into the water and an environmental disaster, it must be designed to high construction standards.

A yacht captain may notice a range of colors in the diesel that is pumped on board when bunkering diesel anywhere in the world. The colors of France, Greece, and the United Kingdom are blue, black, and red, respectively. However, a resourceful engineer should avoid bleaching that fuel and selling it on the illicit market to boost their yacht’s maintenance budget.