Wide Open Throttle

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the last big diesels I bought were 4000 HP and rated for full RPM at 15,000 feet for a 30 minute climb out of an open pit. This is how the engine designers have built most diesels for decades if not 70+ years or more.

These were industrial duty engines.

Many "trawlers" have lawn implement or converted taxi engines , a far far different base engine .

IF there is NO MFG 24/7 power rating , caution is the watchword

FF
 
I read this post 7 years ago when I came into possession of a 26 foot Groverbuilt with a 120 Lehman with 2500hours in it.

I put about 6k worth of parts into it including injectors, head gasket, exhaust manifold, injector lines (no rebuild on injector pump.)

I am religious on maintenance and follow every one in the manual. (Once you do it a half dozen times, you get quick at it)

The engine now has around 5k hours on it.

About 80% of that time has been at wide open throttle. I run it 2500 RPM for hours at at a time. (I make annual runs from NYC to Nantucket, fully loaded with my wife and three of her friends)

All I can say is that it runs like a sun of a bitch and it’s been 7 years of WOT.

Might not last until 10k, but she is gonna run at WOT until the day she dies. (And I will keep doing all the maintenance, on schedule, on her until then)

Just wanted to give an update. I decided to do this based on the continuous rating and the fact it’s naturally aspirated and I don’t have to worry about turbos etc....
 
Greetings,
Welcome aboard speedy.


200w.gif
 
I've had her at WOT one single time and she did 22kts. But she wasn't happy about it AT ALL. (51 year old 327f's)
 
That should be interesting for those afraid to go over 1800rpm.
And even more so those that think higher rpm wears out engines fast.

Got to admit I would have thought the Lehman couldn't do that. But it shows that running properly loaded (prop wise) that running 1900 to 2200 should not be problematic.

Alisske are you sure you're tell'in the truth here? Sorry but 5000hrs at 2500rpm is really work'in that engine!
 
Yes, lol. I’m being straight up honest. To be frank, I had a great paying job until a month or two ago. I enjoy working on the Lehman, and if it blew up, I had the dough to repower.

BUT, things changed recently and the dough dried up, so I started thinking about WOT again, lmao. (Hence googling wide open throttle)

I am going to dial it back to 2300 or something because of my finances. (Got a new job, but 3/4 the pay, so repowering the Groverbuilt needs to wait.

But I did ride that thing WOT for 2 hours today. (Thats when my current dilemma dawned on me)
 
All diesels are NOT the same , sure they work in a similar fashion but the loads they can accept are not the same.


Big Detroits , Cats ,MTU and many others are industrial sourced and can function at WOT , full rated power and RPM on a continious basis.


Big truck engines are similar , just need a few hundred RPM pullback for all day service.


Car , light truck, taxi and farm implement sourced engines can only stand WOT , full power for a very short period of time.


The web site for your engine will usually have 4 power ratings , all are time factore


Should there be no rating , the engine is probably not industrial and WOT operation for a long pei would be avoided.od riod of time should be avoided.
 
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Marin said:
We have had the boat for fourteen years. While we use it year round, my work and other interests pretty much confine us to weekend or three-day trips except for one longer cruise a year. So the boat gets used a fair amount but not for a lot of hours. Most of our weekend trips are three to four hours out and the same amount back.

The engines do not run any differently today than they did fourteen years ago. There is a bit of blue smoke at startup, there is the typical sheen of unburned fuel out the exhaust whent the engines are cold, and that's it. They start as soon as the starter starts to turn them, they run smoothly throughout the rpm band we use, which is idle through an occasional 1800 rpm but mostly 1650. The one time we took them to WOT they did so without protest. The engine temps (coolant temps) are where they are suppose to be at 1650 rpm. We have EGTs and they are marked for the normal temperature at cruise and that's where they continue to indicate at cruise (about 600 degrees IIRC). We have never had to clean soot off the transom, swimstep, or swimstep-mounted dinghy.

The engines use no more oil today than they did fourteen years ago, which is less than one quart per engine every 100-150 hours which is our oil change interval.

All this isn't to say they both won't explode next week but so far the engines have not changed at all.
Click to expand...

That fuel oil sheen on the water, is that something the USCG would see and become very upset and then fine a person for?

Years ago, a guy ran his diesels in the marina harbor for hours and filled the surface of the water with sheen and soot. Of course no official saw this, but at the time I was wondering if they would have considered it a violation of the clean water act.
 
Alisske said:
I read this post 7 years ago when I came into possession of a 26 foot Groverbuilt with a 120 Lehman with 2500hours in it.

I put about 6k worth of parts into it including injectors, head gasket, exhaust manifold, injector lines (no rebuild on injector pump.)

I am religious on maintenance and follow every one in the manual. (Once you do it a half dozen times, you get quick at it)

The engine now has around 5k hours on it.

About 80% of that time has been at wide open throttle. I run it 2500 RPM for hours at at a time. (I make annual runs from NYC to Nantucket, fully loaded with my wife and three of her friends)

All I can say is that it runs like a sun of a bitch and it’s been 7 years of WOT.

Might not last until 10k, but she is gonna run at WOT until the day she dies. (And I will keep doing all the maintenance, on schedule, on her until then)

Just wanted to give an update. I decided to do this based on the continuous rating and the fact it’s naturally aspirated and I don’t have to worry about turbos etc....
Click to expand...

What are your speeds at WOT compared to 2/3 and/or 3/4 throttle?
 
sdowney717 said:
That fuel oil sheen on the water, is that something the USCG would see and become very upset and then fine a person for?

Years ago, a guy ran his diesels in the marina harbor for hours and filled the surface of the water with sheen and soot. Of course no official saw this, but at the time I was wondering if they would have considered it a violation of the clean water act.
Click to expand...


Good grief I hope not... I own a Volvo

:socool:

HOLLYWOOD
 
The Lehman engine was a successful combine, generator, pipeline pump and fire pump motor; they ran at wot in these configurations for years and will attain great life like that. As Marin said once, they were a failure as a truck and bus engine.

We tilt them some degrees, fill them with the incorrect oil level due to mis-marked dipsticks and warm them up for long times at idle. Also, owners are not particular with burping the water jacket nor changing the oil in the Simms. Having said all that, I ran my Lehman up to wot during every run to check temps and pressures and although it sounded very loud, like it might rear up out of the engine room, it ran just fine for the years I owned her. That is actually a clue to why many owners won't do it, they are very loud at WOT and most of us are used to cruising about at lower rpm in the quiet.

Bob Smith told us at his engine seminars that they should be run wot regularly on the way home to ensure they were sound as this was the best way to determine weaknesses and impending failures. Would you rather have a surprise failure when you are mid-cruise?
 
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Xsbank said:
The Lehman engine was a successful combine, generator, pipeline pump and fire pump motor; they ran at wot in these configurations for years and will attain great life like that. As Marin said once, they were a failure as a truck and bus engine.

We tilt them some degrees, fill them with the incorrect oil level due to mis-marked dipsticks and warm them up for long times at idle. Also, owners are not particular with burping the water jacket nor changing the oil in the Simms. Having said all that, I ran my Lehman up to wot during every run to check temps and pressures and although it sounded very loud, like it might rear up out of the engine room, it ran just fine for the years I owned her. That is actually a clue to why many owners won't do it, they are very loud at WOT and most of us are used to cruising about at lower rpm in the quiet.

Bob Smith told us at his engine seminars that they should be run wot regularly on the way home to ensure they were sound as this was the best way to determine weaknesses and impending failures. Would you rather have a surprise failure when you are mid-cruise?
Click to expand...


Well said Xsbank,
I'm not saying it is but if it's true running at 50-70% load should produce a 30,000hr engine. I'm sure (opinion) that running at 50-70% should allow an engine to run much longer than at WOT keeping the temps up and the heavy loads down.
 
Industrial engines usually don't run at full hp load. Lehman generators probably run at 1800. Pumps also rarely run at wot and run at rpms lower than propulsion engines. Once pressure is reached in the line, they only pump enough water to maintain.

I've rebuilt many of engines for people that run at wot. Except for a couple manufacturers, even heavy duty engines have shorter life at wot. Especially engines with turbos. Exhaust gas temp is the killer. It eats away the metal in the hottest parts.
 
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Lepke said:
Industrial engines usually don't run at full hp load. Lehman generators probably run at 1800. Pumps also rarely run at wot and run at rpms lower than propulsion engines. Once pressure is reached in the line, they only pump enough water to maintain.

I've rebuilt many of engines for people that run at wot. Except for a couple manufacturers, even heavy duty engines have shorter life at wot. Especially engines with turbos. Exhaust gas temp is the killer. It eats away the metal in the hottest parts.
Click to expand...

There's a post I believe you can bank on!
 
Full Hp load is RPM dependent, and different for most engines.

The engine in a gen set when rated for a lawn implement might be 25HP at 3000RPM.

But when set to 1800 RPM operation it is no longer a 25Hp engine., perhaps 16 HP .

So 75% or 80% might be 12hp for a constant long term load.

Same with a propulsion engine at reduced RPM, a cruise at 1500-1800 RPM will have its own power limits based on the power at that RPM, nothing to do with WOT HP rating.
 
I've had four 120HP Lehmans in my time, rebuilt two of them , through non engine related incidents.

The only thing I can say IMHO is that running a FL 120 at WOT is a very unpleasant experience on the flybridge for skipper & crew. She roars like a constipated bull elephant, smells & smokes like a dormant volcano ready to blow.

Why on earth would you bother?
 
Lepke wrote;
“Industrial engines usually don't run at full hp load. Lehman generators probably run at 1800. Pumps also rarely run at wot and run at rpms lower than propulsion engines.”

You can’t get to full load at 1800rpm even at WOT. Maybe a hair over half. On an FL you need 2500 to reach full load.

Edit;
Ahhh I see FF cleared this up in post #107.
 
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Andy G said:
She roars like a constipated bull elephant, smells & smokes like a dormant volcano ready to blow.
Click to expand...



Now THAT is funny right there!!!
 
Quote:
Originally Posted by Andy G
She roars like a constipated bull elephant, smells & smokes like a dormant volcano ready to blow.


Tom.B said:
Now THAT is funny right there!!!
Click to expand...

That is funny!

And, simply makes me want to rip out our super smooth running, gentle sounding, clean burning, minimal maintenance required, easy to work on, inexpensive to service, nearly all parts readily available at auto parts store gasoline Mercruiser 255 hp. engines. Then I can throw in a couple of roaring, bull elephant-like constipated, volcanic smelling, smoking diesels as replacements! - I think, NOT!!! Linda would hang me high... if I did that. And, I'd gleefully remain on the noose because I did that!

Happy Boat-Engine Daze - Art :speed boat:
 
Lepke said:
Industrial engines usually don't run at full hp load. Lehman generators probably run at 1800. Pumps also rarely run at wot and run at rpms lower than propulsion engines. Once pressure is reached in the line, they only pump enough water to maintain.

I've rebuilt many of engines for people that run at wot. Except for a couple manufacturers, even heavy duty engines have shorter life at wot. Especially engines with turbos. Exhaust gas temp is the killer. It eats away the metal in the hottest parts.
Click to expand...


Many large diesels (yes, they have turbos, a marvelous add on invented nearly a century ago) installed on earth moving equipment, gensets and pumps run at full rated power for extended periods. Full power though is controlled by the electronics and or governor to limit fuel delivery to the design specs of the key engine components. Full or rated power should not be confused with WOT - diesels don’t have throttles, gas engines do.

I remain puzzled as to why operating an old Lehman at full rated RPM is a desire.
 
Passed on to me by a marine engine expert....

(Pass along)...... there is a difference between "full load" and rated power output. The engine might be rated at 120hp @ 2500rpm but it can be "fully loaded" at any point along the curve. That is the foundation of all those myths and long winded discussions about 'over-propping."
 
The real question is at what HP per liter is it running.
If WOT is 30 HP per liter then it can run forever at WOT. if WOT is 60 HP per liter it won't last anywhere near as long, regardless of the brand.
 
TomB:
IMO that tag should say 'maximum cruising speed". The tag makes it sound like you should run at that RPM
Of course Volvo do want to sell parts.
 
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The full load or max power curve indicates the peak output capability at various RPM.

I thought that any point on the curve would be OK and that was how engines were derated. Tony Athens specifically said no. Derated engines are rated at lower output than the max power curve of the highest output model according to Tony.
 
200 under max rpm is the cruising speed rpm rule of thumb for every commercial operation that I have worked with if they didnt have a specific one in mind.

Didnt always run there, but if we were trying to make a good time or distance we did.
 
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bayview said:
TomB:
IMO that tag should say 'maximum cruising speed". The tag makes it sound like you should run at that RPM
Of course Volvo do want to sell parts.
Click to expand...



I run about 2350 - 2500... that is about 250 - 300 below max rpm because I don’t believe it will wear the engine out at any greater amount than at 1600. I mostly want to go 18 mph and not 10 or less. But that’s just me.
 
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