Question, Are marine diesel engines unreliable

[Peter]

Question for general discussion, why do marine diesel engines appear to be so unreliable, judging by the amount of threads on the forums. When land based diesel, lorries, cement mixers, dumper trucks etc seem to run “forever” with little or no maintenance?

 

[JeremyF]

Cos they get used more frequently than boat ones, so the fuel does not sit gathering water and bugs. Not sitting in salt-ridden damp air helps as well!

Generally marine deisels are good, as long as they get a reasonable amount of care at the beginning and end of the season, and there is a reasonable recognition that a 10 year old engine is going to need an overhaul.

Jeremy Flynn

 

[Twister_Ken]

Lack of use. nm

§

 

[DepSol]

Sorry dont go for the crap fuel answer and as for salt air living on Guernsey the car gets as much exposure to the salt ir as boats do so I dont go for that one either.

Shortcuts in engineering which lead to increased sales of spares and new engines might be a more plausable answer.


Dom


I just want my boat back in the water ;-(

 

[Rob_Webb]

I'm no diesl engineer but here are the key points which I thought were pretty commonly understood about diesels used as auxilary engines on sailboats:

1. Lots of harm done when engine is not being used i.e. corrossion building up due to salty environment. Unlike car engines, these are usually just a few inches from sea water which is often swilling around in bilges. Also, they usually use sea water as coolant hence the comparison with a car engine driven near the sea is unfair - marine engines definitely have a harder life in this respect.

2. Majority of wear done during cool-running i.e. engines hate the cold starts and short runs which are symptomatic of use in a sailing boat, when the engine oil harldy gets a chance to warm up and properly coat the moving parts and protect the thing before it is shut down again.

3. Like all engines, unless they are inherently defective, they prefer to be used regularly and robuslty, with servicing as required. Infrequent, light/hesitant use and dubious servicing will adversely affect things.

In this respect I reckon we probably have something to learn from our motorboat cousins - as a pure guess, I bet that if you did an experiment with two identical engines put in a sailboat and a small workboat, the one in the continuously used workboat would perform better over time than the lesser-used sailboat machine.

 

[Paulka]

On the contrary, I think they usually are reliable.
I had two Volvo - MD2B and MD 11C - which are basically the same engine, and only had one problem which is not specific to neitheer Volvo, nor to diesel engines.
My first engine, I had bought with a second hand sailing boat I kept for 5 years was as good when I sold it than on the first day I've got it.
The second one, I bought new with my current sailing boat in 1979, started to overheat in 2000. As it was then over 20 years of age, and had run for over 2000 hours, I decided to have it completely dismantled, and every part checked.
Here the result:
Main bearings : Big end, all of them inside the spec. small ends, one of them O.K., the other out of spec.
Pistons and liners: one set O.K. - the other: one piston ring brocken, liner out of tolerance (ovalisation).
Cooling water: All water ways in the block, particularly around the liners completely clogged by glas hard yellowish deposit.
Everything else, was in good or very good condition.
Based on those findings, I decided to buy a set of pistons - liners, and to have the crankshaft grinded, and oversized shells installed, just not to have too much of remorses, should something happen in the future!

.... And the engine already has happily run over 400 hours since it was rejuvanated.

The only maintenance I ever did on my engines is oil change, replacement of filters, fresh water flushing 2 -3 time a year. The injectors were checked and adjusted once, after 10 years / 1000 hours.

Thus, I would say: the marine diesel engines are not that bad at all.
BTW, most of them are based either on small truck engines, or on industrial engines. The 2 and 3 cylinders Volvo are very common under another name as pump engines on the oil fields.

Thats just my opinion.

Paul

 

[Joe_Cole]

I don't know if it's true but I seem to remember reading somewhere that Marine engines run a lot cooler than automotive engines and that that affects lubrication and efficiency.

I also suspect that there's far more R&D going into car engines these days. They are far more sophisticated than Marine engines.

Joe Cole

 

[dickh]

Most modern marine engines are based on either an automotive or industrial engine, with the marinising bits bolted on. There are exceptions like Bukh and Sabb which make their engines for lifeboats as well and must be easily hand started. The base engine is usually reliable and it is usually the ancillary bolt on goodies that fail, ie alternators, waterpumps, starters etc. With modern heat exchanger designs they should run at the correct temperature, but some are still sea water cooled and therefore run at a lower temperature; 60ºC max. I believe. As stated earlier, most auxiliary engines barely get hot before they are turned off, they need a good run to keep in good condition and of course regular servicing and correct winterizing. The salt water environment also does not help, corrosion soon starts in tiny places all over the engine and in the wiring if not marine grade. IMHO I think the manufacturers should stick to Non-turbocharged engines for reliability etc. but I can see the argument for Turbo charging as you get essentially the same size engine but more powerful, thus not fitting a larger engine, weight, different mountings etc etc.

 

[billmacfarlane]

Since the purpose of these threads is to air and help solve problems , it might appear that there are thousands of unreliable engines out there but what you are not seeing on this site is the tens of thousands of satisfied customers whose engines don't give them a problem. My own personal experiences of diesels is that they are very reliable .

 

[Guest]

here,here, quite agree........ooh whats that funny burning smell!

 

[Vic]

Are there any statistical reliability surveys on small marine diesel engines like those for automobiles ?
Being the subscriber of PBO and YM I have a feeling that Volvos are the most ureliable type of engine. Other brands are almost not seen in the desperate readers enquiries.
It would be intersting to know what is the market share of Volvo, Yanmar, Nanni,
Vestus and others.

Victor

 

[bedouin]

I think Volvo have had a lot of bad press, much of which is undeserved. For example they have the reputation of being expensive for spares, but a recent survey in one of the yachty mags showed that they were actually cheaper than many of the competitors across a range of service parts and spares.

It seems that for years Volvos dominated the small marine diesel market - it's rare to hear of an engine over 25 years old that isn't a Volvo - so it is likely most of the problems with older engines one hears about will relate to Volvos.

 

[david_bagshaw]

I rather think you have proved the point, in your comment at 2000 hours.... and various items need replacing.

the average commercial trunking truck engine will do 20 hours a day 5 days a week for say 330 days a year for 6 years, ie 198000 hours, then you need to replace large parts of the engine.
on your basis every truck would need a major engine overhaul every 99 days!!! I can just imagine the sniggers in VMU.

even a home delivery vehicle will run 12 by 5 x 330 x 6 =118800 hours with a much worse duty than the trunk vehicleof city traffic , engine on & off etc, with only rare major failures. Indeen at the moment the big problem on our fleet is injection pump wear due to the lower sulphur content of these green fuels. (not very green if it leads to early scrapping of the truck.)

this is drawn from experiance with a fleet of 300+ 7.5 t vehicles (6 &4 cyl engines approx 150bhp & 40 trunk vehwith 8 cyl 240-280 hp) all turbocharged.

David
www.euroboating.net

 

[milltech]

Even finding a spanner to fit is a problem for me so I claim no expertese, but I always assumed that diesel benefits were that a mechanical fuel system allied to a slow revving engine meant that all you had to do was supply fuel. This is why I'm a fan of old engines like Gardners because I worry that modern engines with electronic controls will essentially be as vulnerable as a petrol engine that needs a spark.

Is this prejudice valid?

John

 

[Guest]

I have an old high rated 32hp Perkins 4-99, 'donkeys years' old, low on compression, had easy-start squirted at it for years .....
I fitted my own priming system .... bit of 3/8 tube filled with diesel and pushed onto the priming nipple on the air-intake ... I switch on the glow-plug exactly as directed in the vinatge manual ! for 20 secs ... then hit the key. Starts first time !!

Everyone told me to change the engine when they saw the use of easy-Start etc. and the age of it. Well I'm happy to continue with it - in fact I am thinking of finding a friendly scrap dealer to source a proper priming set-up .....

The original engine fitter / owner decided NOT to fit the priming system and that was back in 1975 !! So poor old dog has had ether shoved up its nose for nearly 30 years !!!! I dread to think what the piston tops and valve stems look like !! Probably explains the low compression !!!!

But it works and I belong to the Don't fix it - if it aint broke !!