A few moments to spare from earning money to pay for the boat ?

[Bouba]

Sheesh. "Both engines" - the guy was talking about the same engine ffs - one engine not two - that is the whole point of the bit I quoted in red. It was the very same engine, run under the same conditions. If you have two of them and compare the 30%-er and the 70%-er the results would be identical. The 30% number arises only due to a different denominator, not any difference in numerator. That's the whole point. If the red part quoted above isn't explain that then it's a tougher thing to explain that I thought.

Rustybarge covers this in post 7. He says the denominator should be the continuous duty rating. For my Cats that is something like 900hp so if I'm pulling 630-720 hp from them that's 70-80% and they will last for ever. In the 1925hp version it would be nonsense to say the best way to run them for longest life is to take 70-80hp of 1925hp.

Therefore your golden rule of running at 80% is fundamentally flawed, unless your engine's max HP is its continuous duty rating, which obviously it isn't because yours are 700hp each from pretty small MAN motors with MAN's typical small/undersized journals. Your continuous duty rating is more like 300hp and if you want to take 80% of any number it should be 300hp. This is what the bit I quoted in red above is saying.

I don't doubt you could corroborate what you say on all sorts of forums and dockside bars, because other people misunderstand this too. Doesn't change a thing.

From your data it appears your cooling system isn't great. On my cats, whether I'm developing 150 or 1500 hp or anything in between, and in 10deg C seawater to 30deg, they ALWAYS run at 80 deg C jacket temperature, period. Same with all my previous boats (Cats C32 x2 and Volvo D12 x 4). I've never had a boat where jacket temp fluctuates as you describe.

I also have always believed that.
One of the main differences between the continuous duty engine and it's much higher horsepower cousins is the turbocharger. If you chose to run at higher speeds for the good of the turbo that's a different matter

 

[Portofino]

Sheesh. "Both engines" - the guy was talking about the same engine ffs - one engine not two - that is the whole point of the bit I quoted in red. It was the very same engine, run under the same conditions. If you have two of them and compare the 30%-er and the 70%-er the results would be identical. The 30% number arises only due to a different denominator, not any difference in numerator. That's the whole point. If the red part quoted above isn't explain that then it's a tougher thing to explain that I thought.

Rustybarge covers this in post 7. He says the denominator should be the continuous duty rating. For my Cats that is something like 900hp so if I'm pulling 630-720 hp from them that's 70-80% and they will last for ever. In the 1925hp version it would be nonsense to say the best way to run them for longest life is to take 70-80hp of 1925hp.

Therefore your golden rule of running at 80% is fundamentally flawed, unless your engine's max HP is its continuous duty rating, which obviously it isn't because yours are 700hp each from pretty small MAN motors with MAN's typical small/undersized journals. Your continuous duty rating is more like 300hp and if you want to take 80% of any number it should be 300hp. This is what the bit I quoted in red above is saying.

I don't doubt you could corroborate what you say on all sorts of forums and dockside bars, because other people misunderstand this too. Doesn't change a thing.

From your data it appears your cooling system isn't great. On my cats, whether I'm developing 150 or 1500 hp or anything in between, and in 10deg C seawater to 30deg, they ALWAYS run at 80 deg C jacket temperature, period. Same with all my previous boats (Cats C32 x2 and Volvo D12 x 4). I've never had a boat where jacket temp fluctuates as you describe.

"Both engines " I mean,t if a choice of a single running @ 30 % or 70 % In two different boats not a pair set up differently in the same hull ?
The identical results in the " red " are rpm and boat speed ,he did not refer to temps in that article .
I,am with you on that it's a great article and the others I posted btw for everyone .

I,am skewering towards correct temps and having EGT gauges as explained and oil temp as well as std pressure btw trying to run them in that zone ,cos I can see that stuff .Don,t need to do any rule of thumb fuel vol calc,s

The MAN cooling is what it is I,am just attempting with this particular instal to follow the book .
Just saying it's not really set up for low rpm or tick over for long -- that's fine by me not bothered .
Regarding its rating it was high @ new 2001 from memory but with the caveat like all leisure Versions of the same block of x hrs ,
From memory only 1000 / annum -- which is not all @ 100 % load they recommend - Some proportion is eg 20 % that's 200 hrs. Some other loads are lower .
It's not a detuned continues duty say commercial ( detuned like the" red " ) so getting a greater % load at said Hp -- which is rated for say 5000 hrs or even lower 10000 hrs .
I,am doing only 80 hrs / year so well within even if with short periods going slow guess say 70 % of the time it's deliberately on 80 % load ----- come on guys it is a sports cruiser looks the part and has the hull ( sorry to drag that old chesnut in ) to enable me to press on .

Yours CAT ,s are more suitable to slower running , don,t seem to overcool - but MAN , s well recent ish like mine do not like low rpm cos they can,t run hot enough -- I can see all three temps fall outside optimum Oil , EGT and water jacket @ low loads .Not sure with MapishM ,s old school ,
I,am not complaining - btw or critiquing others .
Mindful of sooting up --- cos I can see the EGT on my screens and equally mind full of the poorly fitting rings for hour after hour .

What do you reccomend JFM I run around @ -- can you advise me ps ?
1780 rpm isn,t exactly caning them and 27 Knots mean s 30 miles - man maths calc,s per hour it burns a wallet friendly 180 L/r @ 80'% load ---- prop is a big pitch btw

Manual says ideal water temp is 85/86 btw but no higher than 90 , and warns not to run too long at tick over in fact as said turn off after 5 mins no load .

 

[Portofino]

S

Sheesh I've never had a boat where jacket temp fluctuates as you describe.

Next time you drop by -- pop across and take a peak at the Amarti exhaust set up
Could be a back pressure issue - the exhaust is split at low medium rpm it goes out of the rear pipe above the WL at the stern , some will be sucked out as the boat speed increase .
How ever above a certain speed the Venturi effect of his invention later refined means I suspect all of it now considerable over 1500 turbo cut in is being sucked out from the under water - his design btw .
May be as it slows down and the rear stern pipes take over the underwater will not work ,there's no bubbles @ tick over from them then there no back pressure cos of the decent sized stern pipes - so aiding a low 125 EGT at tick over , translates into a lower 79 drop from running 85- 86 water jackets .

As I said come and have a look .
Or my water pump and impeller is a one size fits all from the MAN parts bin -- so overcools the 12.8 compared to the same size part in the 22 and 24 L ?...
or a combo of both ^^^^

Any idea,s ?

 

[petem]

Porto, let me try and explain what JFM is saying in a slightly different way.

I had a 2 litre BMW 116ed generating about 115hp (yup, I'm a cheapskate). The 116ed uses exactly the same block, pistons, crank, etc as a 2 litre 123d.

I used to rag it everywhere I went (0-60 taking a rather lumbering 10 seconds ). Now I was constantly running that engine at 100% of its rating (WOT). Do you think I was doing any more harm to it than driving a 123d at half throttle (60% of its rating) to achieve the same 10 seconds 0-60)?

Pete

 

[Bouba]

Porto, let me try and explain what JFM is saying in a slightly different way.

I had a 2 litre BMW 116ed generating about 115hp (yup, I'm a cheapskate). The 116ed uses exactly the same block, pistons, crank, etc as a 2 litre 123d.

I used to rag it everywhere I went (0-60 taking a rather lumbering 10 seconds ). Now I was constantly running that engine at 100% of its rating (WOT). Do you think I was doing any more harm to it than driving a 123d at half throttle (60% of its rating) to achieve the same 10 seconds 0-60)?

Pete

Very clever:encouragement:

 

[Portofino]

Porto, let me try and explain what JFM is saying in a slightly different way.

I had a 2 litre BMW 116ed generating about 115hp (yup, I'm a cheapskate). The 116ed uses exactly the same block, pistons, crank, etc as a 2 litre 123d.

I used to rag it everywhere I went (0-60 taking a rather lumbering 10 seconds ). Now I was constantly running that engine at 100% of its rating (WOT). Do you think I was doing any more harm to it than driving a 123d at half throttle (60% of its rating) to achieve the same 10 seconds 0-60)?

Pete

Nope --- you are assuming both examples ( no reason to think Otherwise P - in the car example ) that both engines or how ever many variants are running @ optimum temps .You may find the rad size and water pump,s different parts .
As said in the links I posted diesels basically have a linear Hp / fuel burn , 18-20 Hp / gallon or what ever ? so the bigger 123 d out of the same block must knock out more heat -- right
And , this is a biggie adding extra complexity though - I accept through nievety in a polite sense P you car has a gear box and a boat has only one gear the prop pitch -- but s lest not go there just now ,

I am focusing on optimal conbustion temps _ __ with what cards I have in hand - there's no G box on a boat
I,am stuck in top
EGT -- for min sooting up and creation of even Less more life shortening substances -- and trying to operate what I have in a " ring sealing " mode -- which means EGT ,s @ 550 if poss , not 350 or 250 or the dreaded 125 @ tickover - no load for more than 5 mins ---
I realise this stuff is off the radar with what seems most of you guys with CAT , VP Cummings or older MAN. stuff .
Cos you can,t see load n EGT ,s and are doing the old WOT minus 200 rpm stuff
Revisit the links above --- all odd them ^^^^^
Join the dots

 

[MapisM]

Therefore your golden rule of running at 80% is fundamentally flawed, unless your engine's max HP is its continuous duty rating, which obviously it isn't because yours are 700hp each from pretty small MAN motors with MAN's typical small/undersized journals. Your continuous duty rating is more like 300hp and if you want to take 80% of any number it should be 300hp. This is what the bit I quoted in red above is saying.

As I already said, I full agree with all that, in principle.
Interestingly though, the rating differences in MAN 6 cylinders engines are much less than you (and I, before checking!) would think.

The engines Porto has on his Itama are (I think) the 2876LE401, good for 700hp @ 2200 rpm.
Light Duty rating, i.e. "up to 1000 hours of operation per year and up to 20% of time at full load" (MAN statement).

Their Heavy Duty ("Unlimited hours of operation and up to 100% of time at full load") siblings were the D2876LE403, good for 450hp - which seems a LOT, when compared to 700 of the light duty, but that is @ 1800rpm rather than 2200.

Now, according to the (obviously theoretical) prop demand curves of the 700hp version, their output at 1800rpm should be 420hp out of 643 at full load - i.e. 65%
Otoh, Porto is telling us that at 1800rpm he reads an 80% load, which means that the specific prop demand of his hull is, so to speak, more "demanding" than in the generic MAN curves.
Nothing wrong with that - in fact that's to be expected to some extent, with deep V hulls.
Otoh, 80% of 643 translates into 514hp, which btw is consistent with the 180 l/h overall that he mentioned.

And that got me thinking: since the max output of the heavy duty version is 450@1800, is actually Porto, at his cruising speed, stressing his blocks as if he would be running the continuous duty versions at 114% load...?!?

 

[Eren]

I will come up with a very simple question. There are many experienced people here who have been boating for many many years. Have any of you met/seen/came accross anybody who had ruined his engines because of using them under low loads or "a tick above idle" speeds?

Me not. And on the contrary, I have seen many people who have been pootling for many years and stating that they have not seen any bad effects. That has also been my experience in the last 6 years with my CAT C9s as I used to cruise at an area with speed limitation of 6 knots, which is my idle speed.

 

[petem]

And for the record, my water temperature remains pretty much constant whatever revs or load is being put on the engines.

 

[[2068]]

I will come up with a very simple question. There are many experienced people here who have been boating for many many years. Have any of you met/seen/came accross anybody who had ruined his engines because of using them under low loads or "a tick above idle" speeds?

No, but a boat that has been used at these speeds for a long time (e.g. as a river boat for years) might be hiding issues that will only become apparent when you try going faster.
e.g. issues with turbo or cooling system.

 

[Eren]

And for the record, my water temperature remains pretty much constant whatever revs or load is being put on the engines.

Well, the same with me with MAN 2842LE433. I will check about EGT values next time though.

 

[Portofino]

As I already said, I full agree with all that, in principle.
Interestingly though, the rating differences in MAN 6 cylinders engines are much less than you (and I, before checking!) would think.

The engines Porto has on his Itama are (I think) the 2876LE401, good for 700hp @ 2200 rpm.
Light Duty rating, i.e. "up to 1000 hours of operation per year and up to 20% of time at full load" (MAN statement).

Their Heavy Duty ("Unlimited hours of operation and up to 100% of time at full load") siblings were the D2876LE403, good for 450hp - which seems a LOT, when compared to 700 of the light duty, but that is @ 1800rpm rather than 2200.

Now, according to the (obviously theoretical) prop demand curves of the 700hp version, their output at 1800rpm should be 420hp out of 643 at full load - i.e. 65%
Otoh, Porto is telling us that at 1800rpm he reads an 80% load, which means that the specific prop demand of his hull is, so to speak, more "demanding" than in the generic MAN curves.
Nothing wrong with that - in fact that's to be expected to some extent, with deep V hulls.
Otoh, 80% of 643 translates into 514hp, which btw is consistent with the 180 l/h overall that he mentioned.

And that got me thinking: since the max output of the heavy duty version is 450@1800, is actually Porto, at his cruising speed, stressing his blocks as if he would be running the continuous duty versions at 114% load...?!?

Thx P :encouragement:
The voice of reason at last .

The "red " article whilst I too agree like JFM and your self in principle , I think it's a bit naughty in the sense he says he's just switches a chip or something - reprogramming the ECU , .... and nowt else .
Fair enough to keep it simple and make his point re changing load and maintaining rpm and boat speed .
What he skips over is EGT,s and water temps .
The higher Hp must create more heat , or turning it arround the lower rated less heat .
Bringing PeteM,s same block diff Hp back in --- say a 2L 4 cylinder 116 d 118 d 120d and 123d. As I mentioned I very much dought it's just a $ 2 Chinese chip , there will be different induction , turbo. Exhaust , poss water pump and cooling , maybe additional oil cooling between the 116 and the 123 , as well as probably different injectors and beefed up pump .

So returning back your eloquent post ^^^ , the various ratings out of the same block say 700 and 450 , again it's not just a € 2 chip change ,
I think the 450 and 700 have different bits especially the cooling side for obvious reasons .
Which returns me back to optimal running temps ( ring sealing + sooting ) --- hopefully this goes some way to understanding why the same " block " although " stressed " survives , bearing in mind it's designed to survive for only 1000 hrs / year but in reality never see that .
While the 450 variant stuck to a geny in the Antarctic runs 24/7 -365 less a few service days .

@ Eren ---- no you don,t hear a lot about under use issues , but that does not mean it's not going on .
The hrs are tiny by leisure guys and as said if the engines reach the spec temps --- it's fine -- more so with CAT s .

One wonders cross fertilising ( I know bad idea ) from the motor industry at engine / mech survey before a purchase ---- if the engineer --- actually technician more actuate term could plug a lap top in and see ALL the operating deltas,s

I.e. Two identical boats ,both reach WOT at the correct rpm --- as std check etc. both 1000 hrs -- both had a pre sale service for the sea trial .
But the lap top shows how those 1000 hrs have been done and every temp delta etc .

Ferrari dealers plug it in and via telemetry the deltas are all sent to Maranello .
They know how hard you have " canned " it how often it's been up 9000 rpm can see every gear change , every red line , every ESR cutting , work out speed for how long , see it all Clutch wear - the point of contact -- is how hard you take off everything
So two cars identical mileage sat on the forcourt both FFSH -------- one s gonna be liability other is ok .

 

[Eren]

Actually, just like MapisM, I also would like to hear an official comment or warning from the engine manufacturers. I read the manuals in detail, nothing. The only thing that I found on MAN manual says that, the engine must not be idled more than 5 minutes. That is it. Bearing in mind their warranty liabilities, I believe that they would have written about "not using the engine at lower loads for extended periods". And surprisingly, please have a look at how they define"light duty engines" at the below MAN leaflet:

http://www.marinemaint.com/man/V12-1224-1360_light_duty_e_17-11.pdf

Let me copy it here:

Definition of light duty operation:
Annual operation hours: Less than 1.000
Percentage of time at full load: Less than 20%
Average load application: Less than 50%
Particular operation conditions: no wide-open throttle below rated speed

Naturally I take your attention to the red line. The manufacturer expects us to have an average load of less than 50%. And this is fully in other the direction of using the boat at 70-80% loads. Please correct me if I am missing something.

 

[Portofino]

Eren ,
That's a generic para in all MAN light duty ,
Light duty which we all with leisure planning craft have , me , you and guys with Mangusta,s with Arnies .
50 % load for me is just starting to push the bow wave when you go from Hull D to initiate planning .
Assume for you and I can,t see many Gusta,s pootling around a hull D speed skipper conscientiously keeping the load at under 50 % for 1/2 a trip after cruising at 30 knots or what ever .
How ever I can,t really see the same conscientious skipper holding it @ 100 % other than a wot test after an annual or pre sale sea trail .
Never mind 20 % of trip time .
Aside @ Hull D as mentioned and reiterated it's ok if you can keep the temps up .
Water jacket is a cull d sac , if it goes down like mine so what ?
It's the EGT with regards to sooting ,but. That's ok if you do an Italian tune up every now and again ,
According to one of the links ^^^ from Sbmar .

But yes gut feeling is it's pulling the Av down in the other direction - agree - then perhaps if one actually records time wise ,for me last 80 hrs this season , what's spent where ,
Well I saw 100 % once for a 10 mins the day it was put back in after it's annual .
A lot of time I spent ticking over , pootling phaffing @ anchorages, marinas etc .
But yup I set my cruise on around 80 % and I guess a lot of other planning boats wether they know it or not must be over 50 % to plane .
Remember @ the instal , at least the 1 st few have been signed off by MAN .
I think they are being over cautious . - but yup that appears an anomaly -- 1/2 the time @ D speed ,which is the only way 50 load can be achieved by I suspect most planing boats .

Only thing I would say if you do a lot of hrs near the 1000 / year @ D hull or D hull + some load say 40-60 % and the temps .-- never plane it , then just accept like rusty barge ^^^ a overhaul @ 3000 hrs as opposed to 6000 or what ever .
Increase oil change freq to wash out extra damaging stuff that otherwise would not have got past the rings if the EGT ,s were 500 +
How ever if it's running @ correct temps then as advised occasional blast .,

I think the assumption from MAN ( and other engine suppliers ) is they have a menu of duty cycle and via collaboration the engine supplier , designer , builder pick the right one off the shelf .

Ive never seen a warning in a planing boat manual with MANs , saying ( extrapolating the link above )

" spend 1/2 you time or more @ D speed " or words to that effect .Thats would be ridiculous an a par with switch em off after 5 mins tick over
What and just drift aimlessly waiting for gap at a busy fuel pontoon in August --- no body turns em off
And nobody plans a trip with 1/2 @ D and 1/2 @ P --- because they are timing/ logging the % use to the letter .

 

[jfm]

And that got me thinking: since the max output of the heavy duty version is 450@1800, is actually Porto, at his cruising speed, stressing his blocks as if he would be running the continuous duty versions at 114% load...?!?

Yes he is, though it looks like Porto has completely missed that point in his reply to you. Sure there is bigger cooling gear etc in the 700hp version, but it has the same bearing surfaces and piston/cylinder surfaces, and in MAN they are at the weak end of the spectrum to begin with.
Not that it matters and Porto should carry on driving his boat as he chooses. The main point I was making right at the top was that it is rubbish to say "run your engines 70-80% to stop bore glaze", without knowing whether it is the N bhp version or 2N bhp version. And your maths basically prove that.

 

[Portofino]

The main point I was making right at the top was that it is rubbish to say "run your engines 70-80% to stop bore glaze", without knowing whether it is the N bhp version or 2N bhp version. And your maths basically prove that.

Agree
Just to be clear I have not said that , indeed said "I,am not interested on bore glazing "or words to that effect .
See my post # 8 ----- approx 1/2. Way down .

 

[Eren]

Reading all these valuable information from yourselves and the references, my conclusion is that the engines are more tolerant than we think and can be use at rates between tick over to 80%s, provided that some precautions are taken like giving an Italian tune once in a while.

 

[rustybarge]

Reading all these valuable information from yourselves and the references, my conclusion is that the engines are more tolerant than we think and can be use at rates between tick over to 80%s, provided that some precautions are taken like giving an Italian tune once in a while.

Nice summary; the reason for this is common rail multi-sequential injectors that provide exactly the right amount of fuel to stop soot and carbon production in the cylinders at low revs/low heat settings. So to a certain extent bore glazing has been cured with the application of modern ECU technology.

 

[MapisM]

Yes he is
...
And your maths basically prove that.

Glad to hear your confirmation that my reasoning wasn't bonkers, because I actually was a bit in doubt.
The fact that a light duty engine, when used exactly in the same envelope of its continuous duty version, can still produce a higher output and still not get close to its max rated rpm/power, puts this whole debate in perspective. Even more so considering that in this particular case the power difference between the two is less than with many other blocks.

Anyway, my personal conclusion is that I don't know how often I will resist the temptation of pushing the DP at the speeds she clearly likes better, but whenever I will, I sure won't lose any sleep over too low engine load...
...and sorry Porto, but I neither think I'll follow your suggestion to keep props fouled to increase engine load!

 

[Deleted User YDKXO]

Ermm... Actually, the whole point of my previous post was that, in spite of all theories (which I'm well aware of), the engines in my old lady always ran hugely underloaded for their whole 20 years life, and don't seem to have suffered at all.

To be fair though P, in a displacement boat like Ant, I'm betting you never ever tried to run at full rpm because it would have been pointless so you would never have found whether the engines had suffered due to continuous low rpm running. I sit on the fence on this one and I take onboard what jfm and you say but I have had a couple of experiences with boats that may suggest that running at continuous low rpm doesnt do engines any good. I once bought a Fairline Turbo 36 which had been owned by a guy who used it exclusively on the River Thames ie at very slow speed. I bought the boat and moved it down to the Solent and started using it at the speeds it was intended to be used at. Not only did those Volvo TAMD60C engines leak oil all over the bilges through most of the seals but they consumed nearly as much oil as diesel (OK thats an exaggeration!). The engineer who worked on my boat put that down entirely to the fact that the engines had been underworked throughout their lives upto that point. Later in my boating life I bought a Broom 37 with Sabre engines which once again had spent most of its life pottering along inland waterways. Again when I started using it regularly at planing speeds, the engines leaked oil but to be fair those Sabre engines had a reputation for that. So maybe if hypothetically the Cat engines in Ant were removed and put in a 40ft planing boat and then blasted around at 30kts, they might start to show similar symptoms

Btw on Ant, if the engines were so hugely overpowered (and youre right they were!) how was the boat propped? To reach max rpm at max displacement speed or not?

Generally speaking and still sitting on the fence, I run a lot at D speeds these days thanks to my gyro but I still try to ensure I spend a few minutes running at high P speeds every trip just to make sure that the engines do some work. In any case is that not why we buy P boats in the first place?