Marine Diesel Engine Maintenance

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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 .

Why You Should Use a Boat Engine Cover

January 18th, 2008    Subscribe To Our Feed

Just as you should cover your boat when it’s not in use, the same applies to your boat engine and its casing. In many ways, a good boat engine cover is even more important, as the machinery of the marine motor can so easily be damaged by road debris, water, moisture or UV rays.Basic Protection For Your Marine Engine

Road debris caught in a boat engine while it is being trailered can cause major repair bills. UV rays beat down on an engine casing, eventually causing cracking. Water must be kept out of the engine’s intake valves. The right boat engine cover will eliminate these problems and extend the life of an engine.

There are several types of outboard engine covers to choose from, depending on where you keep your boat. In all cases, the size and length of your boat engine cover should match snugly to the engine. Take measurements before buying.

A complete boat engine cover envelopes the engine from the top of the casing to the bottom of the propeller. This is the best cover to use for trailering a boat, to keep pebbles, road trash or any foreign objects from getting into the engine or chipping any of the casing. This is also a nice cover for dry storage, to keep out the maximum amount of dust.

Boat Engine Cover

A half boat engine cover protects just the top part of an outboard engine. This is a practical choice for a boat that stays moored in the water and does not need protection for the propeller and shaft. It will keep the intake valves dry and block UV rays.

An engine carrying case is a soft, padded bag for transporting a small outboard motor. Some are as small as the engine and leave an opening for the propeller to stick out. Others are shaped to hold the propeller as well. If the engine and case are stored under shelter, UV- resistance is not important for this kind of boat engine cover.

Add-Ons

For high-altitude boaters, starting the engine on a cold day can be a challenge. However, for customers like the Canadian Navy and the US Coast Guard, heated boat engine covers ensure rapid starting. A few manufacturers offer these space-age accouterments to the public. Plugs are available in different voltages and will keep an engine nice and warm, whether moored in the water or stored on land.

Wet Marine Exhaust System

December 10th, 2007    Subscribe To Our Feed

Fresh water circulated through the engine jacket is cooled by seawater pumped through a heat exchanger. The seawater is discharged overboard either through the exhaust or directly over the side of the vessel. If discharged through the exhaust, it is known as a wet marine exhaust system.The water is injected into the exhaust system, usually in the form of an injection bend fitted immediately after the manifold. In most cases all the raw water flow is taken by the exhaust but in cases where this results in excessive backpressure, the amount of water injected into the exhaust can be reduced and the remainder piped overboard.

A wet marine exhaust system has the following advantages:

• The exhaust pipe is cool enough to be made of uninsulated fiberglass reinforced plastic (FRP) or rubber.
• The use of a flexible exhaust pipe more easily accommodates the movement of the engine when running.
• the wet exhaust is quieter than the dry marine exhaust due to the silencing effect of the water.
• The wet marine exhaust line is particularly suitable with a flexible mounted engine because it can mostly be made of oil-and-heat resistant rubber exhaust hose.

Many types of mixers, silencers and mufflers are available, which should be fitted only in consultation with the marine engine manufacturer. The design of the wet exhaust system must be such that water cannot run back or siphon into the engine when it is at rest (even when subjected to violent motion such as at an exposed anchorage). Engines installed with cylinder heads below the waterline are more vulnerable. Therefore, an anti-siphon valve (vacuum breaking device) is fitted on their exhaust cooling line, which helps prevent water siphoning back into the engine.

… from Australian Boating Manual

How To Change Your Marine Diesel Engine Oil

November 19th, 2007    Subscribe To Our Feed

You can change your marine diesel engine oil yourself by following these instructions.

Use only a Marine Diesel Engine Oil of good quality.

• 5 liter and 10 liter drums are easy to use and can be refilled with old oil for correct disposal.

• Change your oil and filter at least every 100 hours. Keep spare oil filters on board at ALL times.

Many old marine engines use a lot of oil and will require plenty of spare oil for long passages.

• For good engines—Straight 30 W.
• For worn engines—Straight 50 W.

Always keep plenty of rags, degreaser and oil-absorbent materials on board your boat. This is a messy job. Always clean engine and bilge after oil/fuel filter changes.

Always run a marine engine for about 10 minutes before oil change to heat oil or you will not be able to pump it out, even with a good quality oil sump pump.

Some Fuel Injection Pumps have sumps with engine oil (e.g. Lucas & Sims); this must be changed at the same time as diesel leaks back and dilutes fuel and reduces viscosity—oil level then goes up. This can happen to engine sump on some marine engines with internal return lines.

Removing Filters: Cut open 2 liter milk container, hold beneath filter, remove filter and drop into container, then place this container into a bucket with rag in the bottom. This system will save you some time in cleaning.

Use the same method for fuel filters.

Fitting filters: Smear oil on rubber seal before fitting. Do not fit too tightly

• If possible, fill filter with oil before fitting.
• Check filter is not leaking and oil level is correct after a momentary run.

Many thanks to Laurence Burgin for this article on changing your marine diesel engine oil.

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Credits: Work From Home | Matteo Turchetto | Andreas Viklund