Running a diesel

[RobertMartin]

I live on my boat, so I can run the engine everyday, should this been done when there is no load on the engine other then the alternator, will running it damage the engine, glazing etc??? I was told that a diesel should run as much as possible to keep it in top nick...

Bobby aka Seawolf..
Freedom is the song of your soul..

 

[mtb]

AS long as your mooring ropes can take the strain ,put it in gear and never run the engine without load ,or yes you will end up with glazed bores.
Mick

http://homepage.ntlworld.com/boats
I want a big steel ex trawler / tug v/cheep or swap for tug

 

[Trevor_swfyc]

What about if you have a water-lubricated rubber bearing will this not be damaged if you run in gear while not actually going through the water?.
I assume you are not running the engine for topping up the batteries as you have shore power. You are only concerned with keeping the engine in good running order I'm no expert but most yachts and cruisers are stored ashore for 5 winter months without running. I turn my engine over once a month by hand with the valve lifter active so that the pistons are moved otherwise they can mark the bores. The engine oil is changed before the boat is taken out of the water so that it is in fresh oil, ie no nasty acid or by-products of combustion present.
The good you would do by running the engine daily would be less than the wear and tear damage, obviously if you could plot a graph at some point in time the lines would cross maybe at ONCE A MONTH, someone has probably got this data (Volvo maybe). Without any bore wear/glazing data against non running moisture and corrosion problems data it is just a guess.
With salt water cooling most of the damage is a result of this rather than engine wear especially if you are not going anywhere !!

Its all a worry!!
Trevor.

 

[oldharry]

Recreational marine diesels tend to to be scrapped because of corrosion problems rather than through wearing out, and it is often true that a diesel in regular use will survive longer than one that only has the occasional short run. However, running the engine up daily off load risks severely damaging it.

Firstly as you already suggest, a diesel running regularly on light or no load may suffer glazing of the bores, resulting in reduced compression, poor starting, increased oil consumption and increasing exhaust pollution.

Secondly the engine is very likely to suffer cold corrosion in the vicinity of the injectors, and internal condensation problems i.e. round the valve springs, which can then break with potentially fatal consequences to the engine. Cold corrosion is caused by the sudden reduction in pressure on the fuel at the injector nozzle from in the ordere of 10,000 psi in the fuel line to a few hundred psi in the combustion chamber prior to igniting. The cooling effect is sufficient to prevent the cold fuel from igniting in the vicinity of the injector nozzle, which is then subjected to wide temprature varitoions which it is not designed to cope with, resulting in early injector failure, and possible local distortions of the head by temprature variation, leading to potential gasket failure or cracking. Making the engine work hard ensures all components come up to working temprature and receibe adequate lubrication. Light running will also result in the combustion chamber and exhausts/ turbos etc becoming clogged with carbon. This is why you see fishing boats pounding home at full throttle - its not a race back to the pub, but they are blowing all the accumulated crud in the exhaust and lub systems from the days trolling and making sure everything is thoroughly warmed through.

Although the engine coolant may reach working temprature off load, unless the engine is workjing hard, other parts may not, resulting in uneven warming up, which can induce condensation on the high grade steel surfaces. Valve springs are particularly vulnerable, and being spring steel will tolerate very little corrosion before failing in service, with the potential for dropped valves, smashed pistons, damaged crankshaft, con rod through water jacket, etc etc....

So running up off load daily is potentially the quickest way of destroying your engines!

If you do not intend to move the boat, the safest way to preserve the engine is to lay it up according to the manufacturers instructions, using rust inhibiting oils to avoid internal damage, and preservative sprays or whatever for the engine externals.

If on the other hand you do intend to use the engine on a regular basis for cruising, say every few weeks, then the engine will be perfectly OK in between whiles, although a water repellent spray on the externals will help to preserve things.

Finally, running the engine on load on the mooring may cause problems to the local environment. It is astonishing how large a hole even the wash from a small engine can dig in shallow water very quickly - and how big a mud or sandbank can be built up unexpectedly for you to run aground on next time you try to berth! In a river environment the propellor wash can easily do severe damage to unprotected river banks and so on.

 

[oldharry]

Re: and...

If a cutless rtype rubber bearing is fitted, the prop wash from running at moorings provides ample water flow. In shallow water though, the mud and sand stirred up will be sucked back in to it and cause mayhem....

 

[vyv_cox]

I support all of this, although I would add that the main cause of bore corrosion is the presence of sulphuric acid generated when the engine has not been thoroughly warmed up.

There is no need to start the engine for its own sake. I have a 1982 1.6 litre diesel VW camper back home, it is on a battery charger that comes on once per week and it stands for the majority of its life. We only get home a couple of times per year and the engine starts first turn of the key every time. There is no evidence that it suffers at all from this treatment.

 

[romany123]

Nice post Harry
Think I need to keep you in my engin tool box.

Dave

 

[oldharry]

As long as it has a well stocked bar.....

 

[romany123]

Yup
but only after servcing my engine..... otherwise I may have a duff bar and a duff engine. lol

Dave

 

[oldharry]

I was going to suggest that a laid up marine engine is more prone to damp than your camper, Vyv, but looking at the weather lately I'm not so sure!

 

[vyv_cox]

My garage is much colder and damper than my bilges! Garage is old, stone/brick built, plenty of "natural ventilation", up in the hills in N. Wales. Bilges are bone dry, hull is foam insulated and there is a 500 Watt heater on board throughout the winter.