Marine Diesel Engine Maintenance

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Safe Boating Course

July 26th, 2008    Subscribe To Our Feed

Keeping family and friends safe on the water should be of paramount importance to any boater. All new boaters should consider a boating safety course before they head out on the water. Even long-time boaters will benefit from taking a boating safety refresher course.

For those in New York, New Jersey or Connecticut Boating Safety America is a premier source for a safe boating course.

At their website you can find class locations and register for a boating safety course, learn about current Federal and State boating laws, together with meeting the State and Federal requirements for operating a vessel or personal watercraft in the above areas.

The Mechanical Cycles Of A Marine Diesel Engine

July 9th, 2008    Subscribe To Our Feed

Most reciprocating piston internal combustion engines work on one of two mechanical cycles—the four-stroke cycle or the two-stroke cycle. Marine diesel engines work in the same manner. The cycles designate, in correct sequence, the mechanical actions by which (a) the fuel and air gain access to the engine cylinder, (b) the gas pressure (due to combustion) is converted to power, and (c) the burnt gas is expelled from the engine cylinder.

The basic four-stroke cycle marine diesel engine

From the name, it is obvious there are four strokes in one complete engine cycle. A stroke is the movement of the piston through the full length of the cylinder, and, since one such movement causes the crankshaft to rotate half a turn, it follows that there are two crankshaft revolutions in one complete engine cycle. The four strokes, in correct order, are:

1. The inlet stroke. With the inlet valve open and the exhaust valve closed, the piston moves from top dead center (TDC) to bottom dead center (BDC), creating a low-pressure area in the cylinder. Clean, filtered are rushes through the open inlet valve to relieve this low-pressure area, and the cylinder fills with air.
2. The compression stroke. With both valves closed, the piston moves from BDC to TDC, compressing the air. During this stroke the air becomes heated to a temperature sufficiently high to ignite the fuel.
3. The power stroke. At approximately TDC, the fuel is injected, or sprayed, into the hot, compressed air, where it ignites, burns and expands. Both valves remain closed, and the pressure acts on the piston crown, forcing it down the cylinder from TDC to BDC.
4. The exhaust stroke. At approximately BDC the exhaust valve opens and the piston starts to move from BDC to TDC, driving the burnt gas out of the cylinder through the open exhaust valve.

For more help with your marine diesel engine grab your copy of “Marine Diesel Engines For Beginner“

Marine Diesel Engine Troubleshooting

June 22nd, 2008    Subscribe To Our Feed

Marine Diesel Engine Troubleshooting

If your marine diesel engine fails to start it could be for any of the following reasons…

Engine does not turn over:

• Totally flat battery
• Battery connections or fuses
• Faulty switches (battery and starting circuit)
• Starter solenoid
• Starter motor
• Engine locked up –– water or oil in cylinder (or seized up)

Engine turns over but does not fire:

• Fuel is shut off / no supply
• Low cranking speed: engine in gear; auxiliary equipment engaged or low battery charge
• Cold weather thickens the oil in the crankcase (turn the engine over a few times) also affects
battery cranking efficiency
• Engine in poor condition – low compression – too cold
• Poor fuel injection
• Check engine stop control has been reset
• No air – emergency shut down stopping air (GM two strokes)
• The pre heater (glow plugs) not operating
• Air or water in fuel

Marine Diesel Generators

April 24th, 2008    Subscribe To Our Feed

Marine diesel generators represent a major and very expensive part of outfitting any commercial or pleasure craft. In the process of selection you need to accurately identify what your power needs will be on board and then look at the available marine diesel generators that can meet those needs. Marine diesel generators can be turbocharged with fairly simple and inexpensive modifications if needed. In contrast, gasoline powered generators cannot pump out a comparable power increase without expensive and intensive alterations. A marine diesel generator often runs at only 60% - 70% of its rated power. Under these conditions some engine builders recommend a 20 base number oil.The folks at Poweredgenerators .com do not consider diesel generators the best option for residential applications. They believe that natural gas or propane are much better options. There are some available brands out there but potential customers should first look at other options for residential backup generators. Power outages have been known to last up to a month, particularly in those areas that are prone to tornadoes or hurricanes. Trying to survive all this time without some form of emergency power in the form of a backup generator is difficult to imagine, and those in remote areas will feel their isolation even more.

Marine Diesel Engine Oil Systems

March 13th, 2008    Subscribe To Our Feed

Marine Diesel Lubricating Oils

The marine engine lubricating oil does not merely lubricate the moving parts, it also performs a number of specific functions.

1 It forms a film between the moving parts, preventing metal-to-metal contact. As a result, wear is kept to a minimum, power loss due to friction is minimized and engine noise is kept to a low level.

2 It acts as a cooling agent by carrying heat away from hot engine parts.

3 It forms a seal between the piston rings and the cylinder walls.

4 It acts as a cleaning agent.

5 It resists the corrosion of highly-polished engine surfaces by the acidic products of combustion that enter the sump past the piston rings.

To efficiently fulfill these requirements the marine lubricating oil must posses a number of important properties. Of these, viscosity is one of the most important, and has already been defined as the reluctance of a fluid to flow. A fluid with high viscosity may be said to be thick or heavy, while a fluid with low viscosity is said to be thin, or light. Fluids tend to become less viscous as they are heated and, conversely, to become more viscous when cold. An engine oil must not become so thick in winter as to cause starting difficulties, but must not become so thin at operating temperatures as to fail in its requirements as a lubricant.

Because deposits and acids are formed through the combustion of fuel, and the marine engine oil should have the ability to wash the deposits from engine components and to neutralize the acids. The oil should not foam when agitated in the sump and should be able to withstand the extreme pressures encountered between certain engine components.

Mineral oil, by itself, cannot fulfill all the requirements of an engine lubricating oil, and certain chemicals are added it.

In the example at right, oil is pumped by a positive displacement pump which is driven by the engine to circulate the oil through the system.

Alternatively, some old engines are splash type where oil is thrown around the sump by the crankshaft scoops.

You can find a ton of information on marine diesel engines in the downloadable e-book Marine Diesel Engine Basics. You can print out your own copy, insert the pages into plastic covers and take it with you when you work on your engine. It is a highly recommended book. Buy your copy now!

 

How To Bleed A Marine Diesel Fuel System

February 5th, 2008    Subscribe To Our Feed

Bleeding The Fuel System in a Marine Diesel Engine

To bleed the fuel system, or part thereof, means to remove all the air from the fuel lines and chambers in the system. This is done by pumping fuel through the lines and venting the air/fuel from various bleed points in the system.

A fuel system will need to be bled after changing the fuel filters, running out of fuel, if there is water in the fuel, if there are loose connections causing air leaks, if you have taken on poor quality fuel, or if there is bacterial growth in the marine diesel fuel tanks.

Always follow the correct progression of bleeding as shown in the diagram. To pump the fuel you must first operate the lift pump to bleed the low pressure side of the system. The lift pump must be pumped many times to ensure complete bleeding. Ensure your lift pump works well. Aftermarket bleeding pumps can be fitted.
If pump does not operate (that is, the lever is slack), check if rocker arm is depressed. Turn engine over and try again.

First bleed primary filter by loosening bleed screw on top of housing. Holding a container under filter, pump fuel until no bubbles are visible and fuel is running freely (that means it’s going everywhere!). Tighten bleed screw whilst pumping. Repeat process on engine filter and fuel injection pump. Put throttle wide open in neutral and crank over engine for 25 seconds. If engine won’t start, crack one or more injectors until fuel leaks out, then tighten whilst cranking over engine. If engine still won’t start, repeat entire bleeding process.

Have plenty of rags and fuel clean-up equipment on hand. This is a messy job. Put oil-zorb pads in bilge. Oil-Zorb sheets are available online from BoatersWorld.

This information on bleeding a marine diesel fuel system is an extract from the downloadable e-book “Marine Diesel Engines Basics” available from www.marinedieselsecrets.com .

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Copyright © 2008 Marine Diesel Engine Maintenance

Credits: Work From Home | Matteo Turchetto | Andreas Viklund