Diesel engine likes to run hard…

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cmedsailor

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I am a bit confused with this “general accepted comment” (if I am allowed to call it like this). My Volvo Penta MD2030 has maximum rpm of 3400 (I have tested it on calm water many times) and it is according to manual’s WOT range (3200-3600). The manual also states that cruising should be 300-500 lower than maximum. But even 2900 rpm sounds too much. I usually cruise at 2400 to maximum 2600 and the engine sounds and feels nice. At that rpm burns approximately 3 litres per hour which is normal for this engine.
What’s your opinion?
I also know that from time to time it’s good to use WOT. But what does that mean? How often, how long and when (after cruising for some hours? how many?)?
Thanks
 
Cannot speak for Volvo but Sabre reckon 200 rpm below max is good for cruising, providing you can pull max as stated in the book, " ticking over" revs is bad so they say.
 
I've got a 2030 in a 10m boat. I'm told I can run it at any speed, just so long it is working ie. driving the prop.

It is rarely asked to run above 1900rpm. Noise and all that.
 
You are doing just fine! 2400-2600 is cruising revs/speed. Bit surprised if you are using 3L an hour at that speed - should be nearer 2L. Have a look at the fuel consumption curves and do the sums.

As to WOT, my old Yanmar handbook used to recommend (from memory) up to 1 hr in 24.

BTW when we chartered our boat with a 2030, we set an advisory limit of 2600. Engine has done over 2500 hours and runs perfectly.
 
There is a lot of misunderstanding surrounding this subject. Run it hard does not equal thrash the bejezus out of it. What you should not do is run at low revs with low load or run for short periods at any load so the engine does not reach proper operating temperature. Even this is not a "never do so" thing. Just don't do it all the time and if you have had a period of running like this a good blast at high revs for an hour or so will be good. If you are running between 1/2 and 3/4 throttle and the engine is reaching it's operating temperature for at least 1hour at a time there is nothing to worry about.
 
The problem can be the difference between what is ideal and how we use our boats. Many people just use the engine for getting in & out of their berth, say, 10 minutes. I usually try to give the engine a run until reasonably warm at least, say, 20 minutes at cruising speed.

Another difficulty is motor-sailing, Sailing yachts these days have much larger engines than the "auxiliaries" we used to enjoy, and this often means that we run the engine quite lightly for something like a cross-Channel trip of about fifteen hours. I don't know what the answer to this is, unless we tow a drogue to make the engine work more (!).

For 2030 owners - I can reassure them that I've run mine at 2,700 rpm continuously for 24 hours without a problem.
 
Yanmar's workshop manual for the 3GM suggests as follows:

When operating the engine at low speed for a considerable time, race the engine once every two hours. Racing means taking it to maximum revs, in neutral, then back to tickover, about five times. This blows carbon deposits out.

When under way, periodically operate the engine at near maximum revs. Also intended to blow out carbon deposits and increase exhaust temperature.

The engine is designed for maximum throttle operation, 3600 - 3800 rpm, for less than 5% of the time.

It is designed for cruising speed, 3400 rpm, for less than 90% of the time.
 
Our 27 year old MD21B has rarely gone above 2000 revs, in fact not that often above 1500rpm.

Seriously, I wouldn't worry about it. Run your engine as you wish, and if you need to renew it after 20 instead of 22 years, well so be it.
 
Full power and old wives tales

As others have suggested, for maximum life engines should be run at design temperature, using fuel of correct quality, with fuel combustion in good order and good lubrication to the designed specification.

In pratice engines can rarely be run to satisfy all these conditions all the time so it has become a bit of folk law to say run engines hard now and then to ensure it gets hot and burn off carbon deposits etc. I am suspiscious of this having overhauled many engines large (30,000 hp 2 stroke slow speeds down to single cylinder 4 stroke 2 hp ) if running hard does burn off much carbon except after running with very poor combustion when yes I have seen many engines clean their exhaust systems, but by having actual exhaust fires on subsequent full power runs rather than blowing caked on deposits out.

If your engine is in good condition with good combustion I would not worry, it will last many years anyway.
Ronhilda's engine is 22 years old now and does not get 'threshed 'at full power and has never had the head off. The injector tips are 14 years old since the nozzles were changed. Still starts in freezing temperatures on tick over, does not smoke or overheat. All I do is check the timing belt at 4,000 hours check the oil condition every year and monitor oil pressure, water temperature and for signs of poor combustion. I get about 5-7 years between oil changes. Yes - needing oil changes every year 'because the oil will go acidic' after a few hours running is another old wives tale.
Brian
 
Ooh, please Sir, can i join in? I have a Beta 14 (2003) in my Colvic 26, just done the heat exchanger cleanout which it certainly needed, as the anode had crumbled and blocked half the channels, sorted now; I was wondering about the revs/use equation 'cos according to the Beta download of torque/power/ fuel consumption, it appears that running the engine at about 26/27 hundred rpm gives the best balance. However, a coupla weeks back while practising pontoon approach manouevres, I decided that it would do no harm to give the engine a workout at full power, as per some of the replies above........which incidentally is how I discovered the overheating due to restricted raw water flow.........I couldn't get the engine to go over 3 k (it's rated to 3600), so I'm presuming that the engine was working at full load..........and I'm overpropped. So I guess that at 3k, I'm putting the engine under full load, (no smoke though) so am I OK just running it at 3k occaisionally? Also, inref to Brian Humbers post re oil change intervals, I'm reminded of 10 years ago when I was learning to drive big rigs at Riverside, Los Angeles and asked how far the rigs went between oil changes........they said they routinely went to 40,000 miles between changes. Bit of a jaw drop there and I said what precautions do they take in the meantime, to which the instructor said 'dont run at idle for more that 15 minutes, so if you're using the engine to warm the cab up, run at 1100 rpm or you get fuel contamination of the oil'. This was Schnieder (sp?) so I guess they knew what they were on about......but wow, 40k 'tween changes. I'm not sure I'd do that myself....
 
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We have run our Beta 13.5hp at idle for seven hours then absolutely flat out in heavy seas for three and a half hours immediately afterwards. We have also run it for three days continuously. If the cooling and oil is OK I don't think it matters at all. I do try to change the oil once a season or every 100 hours.

- W
 
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cmedsailor said:
I am a bit confused with this “general accepted comment” (if I am allowed to call it like this). My Volvo Penta MD2030 has maximum rpm of 3400 (I have tested it on calm water many times) and it is according to manual’s WOT range (3200-3600). The manual also states that cruising should be 300-500 lower than maximum. But even 2900 rpm sounds too much. I usually cruise at 2400 to maximum 2600 and the engine sounds and feels nice. At that rpm burns approximately 3 litres per hour which is normal for this engine.
What’s your opinion?
I also know that from time to time it’s good to use WOT. But what does that mean? How often, how long and when (after cruising for some hours? how many?)?
Thanks
Click to expand...

Consider how much more experience we have of diesel engines in civi street - all that acceleration, running the engine up and down the scale, short runs to the shop, followed by many periods of idling waiting for the kids, leading to coking up....

So everywhere you hear - "I'll have the 10k service for my car, and de-glaze the bores, please"

Doesn't happen does it? Civi street diesels seem built for it...fit for purpose etc. So what makes marine diesel applications so different?

I've been pushing diesel powered boats around, quite a lot, since 1985. The occasional burst of "cleansing power" satisfies the urge to keep the "pipes clear" but probabaly and seemingly has no mechancial effect whatever. I suggest you rid yourself of angst in much the same way and enjoy your time at sea, leaving others to pound on about minor issues.

And they will.

PWG
 
An good example of an engine running without enough load is the yanmar 1gm10 on kingfisher, run for too long without enough load on the generator and the bore glazed up leading to large amounts of oil being used, after contacting yanmar agen she was advised to use cooking oil which she did and this did the job !

this was told too me by my local yanmar agent who gave the advise personaly
 
I have a 2030 - oil changed every year. Generally run at about 2500 rev.

When I launched this year I was advised to take the boat for a trip, increase the revs, put a load on the engine, rather than run the engine on the mooring otherwise glazing can happen - whatever that is ?

Must admit I've never really considered any of this - I hardly ever run the engine on tickover. Its usually cast off, increase revs to around 2500 which gives reasonable pace and smooth running.
 
PeterGibbs said:
Consider how much more experience we have of diesel engines in civi street - all that acceleration, running the engine up and down the scale, short runs to the shop, followed by many periods of idling waiting for the kids, leading to coking up....

So everywhere you hear - "I'll have the 10k service for my car, and de-glaze the bores, please"

Doesn't happen does it? Civi street diesels seem built for it...fit for purpose etc. So what makes marine diesel applications so different?
Click to expand...

Well the difference according to many sources is exactly what you have described. Engines that experience varied revs throughout their life last significantly longer than those that run at constant revs for long periods. Hence the Yanmar advice to give it a blast now and again.

The practice of running the engine flat out for a couple of miles is one widely used by boatyards. Owners are mostly completely satisfied with the increase in performance and smoothness and pay £100 for the pleasure.
 
I was advised to take my beta 38 up to the black smoke limit once it was well warmed up for at least a few minutes every time I went out. Other than then it usually sat at around 1600 revs.
 
Another good reason for running the engine flat out occasionally is to prove that it can handle it. With these Spring tides you may need full throttle to make any progress over the ground!

When I run the engine in the berth I usually run it in gear in reverse at 2,000rpm. (Only if it's not going to annoy anyone) I rarely go above 2,500 rpm when motoring.
 
btw, you get maximum torque, which is usually what you need for manuevering, at perhaps half to two thirds your max revs
 
Oooh! there are some old wives tales on here.................

Thrashing,WOT, working temperature ect.

Lets look at a large generator engine....... 6ltr driving a generator, it will probably run around 1800 revs, which will be about 2/3 of it WOT and as such will run for 10s of thousands of hours. The reason for this is that the cylinder temperature is high and therefore completely burns the fuel. (lets not split hairs here)

An engine that is run for only a couple of hours lightly will, although water temperature readings will say it has, not get the cylinders to their maximum working temperature and therefore some residue from the fuel will remain, that will be what we call "Soot".

In order to get the cylinders to correct temperatures you either have to run for extended periods (many many hours) or as manufacturers recommend, run the engine at WOT for certain periods of time. For most and due to the type of cruising that most owners do running at Wot for a short period raises the cylinder temperature to remove carbon products and keeps the inner engine clean (er)

OK laymans explanation with out baffling people.

Tom
 
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