Running my engine hard?

[four winds]

I think bad habits have led to the replacement of more than few Yanmar exhaust elbows. And the idea that it is a consumable item like a fuel filter. I dont agree.

Some paraphrased comments from the Yanmar 3gm30 manual, from memory. I've read it cover to cover.

Full rated power/rpm is allowed for one hour. For use when conditions warrant. I did this once for 45 minutes running from three water spouts that lasted longer than I expected.

Continuous rated power/rpm is allowed indefinately.

For every four hours the engine is run below continuous rated speed run the engine at full rated speed for thirty minutes.

Before shut down let the engine run at idle for five minutes. Then raise the speed temporarily to full rated speed and pull the fuel stop. This implies shutting down at full speed. But I don't. I let it slowly back to idle then fuel stop.

If the engine is shut down immediately after full load operation. The engine parts will heat up quickly, possibly causing damage.

That's all I recall from memory. I'm a manual geek.

Seems my relatively high revving mechanical diesel needs to be "blown out" regularly. And prefers to be run at full continuous load if possible. If not done so, specific instructions are in the manual to be followed.

I try to follow the manufacturers advice in this.

Maybe the best of advice from some of the ancient mariners here is a bit outdated.

[Lepke]

I've rebuilt or overhauled dozens of diesel engines in my life. Mostly HD engines, but a number of recreational engines, mostly US or British. I also operated several dozen, in the military, for others and mostly my own since the mid 70s. As an operator I ran engines at about 80% of hp, considering above that to be emergency power.
I have seen the insides of worn and failed engines and usually had some knowledge of how they were operated and maintained. Engines used at about 80% have a much longer life. Especially turbo models. Blowing out the carbon in an old engine usually doesn't end well. It builds behind the rings and tends to keep the rings tight to the sleeves/cylinder. As the carbon burns away it can make the rings loose in the bore and a good old engine can become an oil burner. On valve engines loose pieces of carbon can embed on the valve or seat face. The valve/seat can burn before the carbon piece is burned away. Also there can be metal fatigue in parts that isn't challenged at lower hp.
On the other hand, engines run long hours at light loads like some generator engines or main engines running high rpm , for battery charging, but not in gear will glaze the walls of the sleeves/cylinders leading to lower compression. I've seen it happen in under 1000 hours.

[wesevans]

Yes it is true. running your diesel at max rpm for 30 minutes occasionally will alert you to problems that will not surface at normal operating RPM untill they become serious. (Cooling, oil pressure etc.) Also it will help remove carbon build up. It is a good policy especially if you have run the engine at low no load (Idle) rpm for extended periods. Check your operators manual as some engines should no be run at max RPM for extended periods of time.

[knockabout]

most diesels thrive on hard running once they are at operating temperature / crank the throttle up to full back it off a little bit (5%) give it a good run for half an hour. all gauges should stay in normal range under full load / makes up for thousands of hours set on high idle with full sails up motor sailing in cast iron main driven apparent wind / once a month should be enough to help stop glazing in the bore from light use

[trantor12020]

Originally Posted by Transition

Hi, .... long trips to just run steady at around 1900 rpm. ....

From all advise I've been told, never to run a diesel on a single rpm for prolong period. It'll cause glazing of cylinders wall. For long trip run at different rpm for a period like say 1600rpm for 2 hours then 1900rpm for 2 hours then progressing higher and lower. You'll also need to run at max rpm for say 1/2hr to blow out and carbon build up. Its just a suggestion.

[Jim Cate]

Originally Posted by trantor12020

From all advise I've been told, never to run a diesel on a single rpm for prolong period. It'll cause glazing of cylinders wall. For long trip run at different rpm for a period like say 1600rpm for 2 hours then 1900rpm for 2 hours then progressing higher and lower. You'll also need to run at max rpm for say 1/2hr to blow out and carbon build up. Its just a suggestion.

How do you explain diesel gen sets that run for thousands of hours, always at the same governed RPM? They don't get the dread glazing, do t hey?

Jim

[reed1v]

Originally Posted by knockabout

most diesels thrive on hard running once they are at operating temperature / crank the throttle up to full back it off a little bit (5%) give it a good run for half an hour. all gauges should stay in normal range under full load / makes up for thousands of hours set on high idle with full sails up motor sailing in cast iron main driven apparent wind / once a month should be enough to help stop glazing in the bore from light use

That differs from what we were told by a Perkins' engineer in a training session put on by our club.

[TeddyDiver]

Part 1

Originally Posted by TeddyDiver

The more suitable is pyrometer to find the exhaust gas temperature. At optimal loading it should be around 600 deg C or 1100 deg F, + 10% can be considered as safe. When running low loads for longer period time to time getting up to optimal loading keeps the diesel engine happy.
http://bankspower.com/techarticles/s...t-is-important

BR Teddy

Part 2

Sorry but some of you don't know what you are talking about. The acceptable loading of the engine is also related of the duty cycles. https://cumminsengines.com/ratings-and-definitions . The very same engine has different rated top hp and rpm depending of the duty cycles and so are the limitations how long periods can be run at max load.
Glazing https://coxengineering.sharepoint.co...reglazing.aspx

BR Teddy

[reed1v]

Originally Posted by TeddyDiver

Part 1



Part 2

Sorry but some of you don't know what you are talking about. The acceptable loading of the engine is also related of the duty cycles. https://cumminsengines.com/ratings-and-definitions . The very same engine has different rated top hp and rpm depending of the duty cycles and so are the limitations how long periods can be run at max load.
Glazing https://coxengineering.sharepoint.co...reglazing.aspx

BR Teddy

Thanks. Perkins recommended three quarters rpms loaded for a "typical" cruiser making way under power. They did warn against the notion of a wide open throttle for any length of time, especially unloaded. But most of the posts are from vastly more experienced mechanics than you or me, or even the manufacturers.

[model 10]

I took it from that great article on glazing that when charging batteries, put the pedal down right away, in gear.

[Stu Jackson]

Originally Posted by a64pilot

This is another reason why I believe you should every now and again operate at full throttle, cause if you can't get full RPM, that tells you your prop and or bottom is fouled and by running at normal cruise RPM, it's actually working the engine a lot harder than it does with a clean prop.

I agree wholeheartedly. I run at WOT every time I take my boat out. After a hull cleaning I get 7.7 knots in flat water with no wind.

I consider this an IMPORTANT benchmark.

Before my next quarterly bottom cleaning, I usually get anywhere from 6.8 to 6.5 knots.

If it is significantly less than that, I have some sleuthin' to do.

[a64pilot]

Originally Posted by Jim Cate

How do you explain diesel gen sets that run for thousands of hours, always at the same governed RPM? They don't get the dread glazing, do t hey?



Jim

Jim they actually can, if not run under a load. Lots of standby generators that are run every so often, but not brought online so they are under a load end up with what is called wet stacking or Diesel slobber, and glazed cylinder walls.
Now if run under a load, well then they get up to operating temp and then it doesn't happen, and even though they do run at one set RPM that never varies by much, the load does vary and the effect is similar to varying RPM, cause with varying load, comes varying cylinder pressure.
Remember with a normal boat and a fixed pitch prop, RPM and load are very closely tied together, you can't load one up without increasing RPM.

Usually the prohibition of constant RPM is for a new engine or a newly rebuilt engine, and it's there to seat the rings, to seat rings you need high cylinder pressure, and that comes with load. High pressure blows the rings out against the cylinder wall and cause them to "seat".
Properly propped, and if run at an RPM that will allow the engine to come up to full operating temp on a broken in engine, long term constant RPM should hurt nothing. My boat spends probably 99% of its engine only cruise RPM at 2000 and so far, no harm, I will motor sail with as little as 1000 RPM though.



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[tkeithlu]

In finding that "sweet spot" on your tachometer you may be dealing with more than the engine and the load the propeller puts on it. All physical objects have harmonic frequencies; the Empire State Building has one at about 7 minutes and some part of my boat has one at about 1600 RPM. Car manufacturers are pros at getting the harmonic frequencies of body panels outside the hearing range; that's one reason cars are a lot quieter than they were in the 1950s. Your boat or part of it has one, and will vibrate harmonically if you run your engine at the right (wrong) RPM. Deadening fiberglass panels is really difficult.

[markpierce]

John Deere says not run my 4045 at idle for more than five minutes at a time, and run it well once a week.

My mechanic says to run the engine "hard."

[Jim Cate]

Originally Posted by markpierce

John Deere says not run my 4045 at idle for more than five minutes at a time, and run it well once a week.

My mechanic says to run the engine "hard."

That's interesting! I wonder if the good folks at JD believe that farmers and construction workers treat their engines like that? Five minutes? Can't even drink a cup of coffee in that time frame!

Jim