2008 PHANTOM 50 FUEL BURN?

[Portofino]

@ MapishM We are all agreeing with Johns calcs / assessment .Just arriving from different destinations.It healthy it’s called convergence.

FYI on my boat @ 18 tons + fluids 2000 l fuel , 500 water so a 2/12 ton floating variance .
Theses are my figures to compare with your heavier / beamy , more drag ( UW surface area ) ….as a matter of interest .
For you in L / Nm .


180 / 28 knots = 6 L / Nm …… 1750 rpm Load 75 %



190/30 . Knots = 6.3 L / Nm ……1830 rpm load 80 %



200/32 knots = 6.25 L / Nm ……. 1900 rpm load 85 %

Very rarely go over 1800rpm or under 1700 rpm loads in the seventies % conducive with longevity.

We haven’t got the Op s load figures only the “1900 rpm “ makes 23 .6 kn from post # 5 .

So filling in the dots to cruise @ 25 knots he s gonna need the imho thrash then N or 2000 rpm and exceed 80 % load ( ok take my 80 % rule as you wish ) .In this area as JFM correctly inferred he gonna be nearer 8 L / nm than the 7 in that hull .Which still works for him with a 1/4 tanks left or there a about s .

It’s nice if you can set cruise on load not speed , it’s what I do and many professionals- American sport fishers racking up 1000 of hrs typically 5000 per annum.= it’s a longevity issues .

 

[jfm]

Not sure why you think people want all that data on your itama again, when we're talking about another boat, but whatever (yawn).

Those sports fisher guys are usually talking garbage, as is very common on US forums. Running an engine based on load % and thinking you're all good because you're on 75% load is just plain ignorance. A 75% load factor on one particular engine in a range might be 100% load on another version of the same engine and 50% of another version, so how can that 75% ever be "right" or "sensible? All this is just garbage spoken by non-engineers.

Simple example = MTU 2000 series 16v. Comes in 2200, 2400, 2600 versions, only difference being ECU and mapping. So you buy the 2600hp and run at 75% load, smugly taking 2000hp out of it. Well, that's the same size of combustion explosion/bearing wear per rev/whatever, and same rate of work done, as running the 2200 hp version (same engine) at 90% load, which all of a sudden doesn't look so clever if this is the religion you believe in.

So if you run the 2200, 2400, 2600hp versions all at 75% load, the bigger engines will wear out faster AOTBE because, if you don't allow yourself to be duped by dashboard load % readouts, you will see that the bigger engines have (in truth) a higher loading than the 2200hp version. Seen through the eyes of the internal components of the 2200hp engine, the 2600hp engine's load% is about 90%, even though its dashboard says 75%. The 2600hp boat's dashboard only reads "75%" because the denominator has been played with. Don't be fooled (or, in your case, try becoming unfooled).

 

[Portofino]

Not sure why you think people want all that data on your itama again, when we're talking about another boat, but whatever (yawn).

Those sports fisher guys are usually talking garbage, as is very common on US forums. Running an engine based on load % and thinking you're all good because you're on 75% load is just plain ignorance. A 75% load factor on one particular engine in a range might be 100% load on another version of the same engine and 50% of another version, so how can that 75% ever be "right" or "sensible? All this is just garbage spoken by non-engineers.

Simple example = MTU 2000 series 16v. Comes in 2200, 2400, 2600 versions, only difference being ECU and mapping. So you buy the 2600hp and run at 75% load, smugly taking 2000hp out of it. Well, that's the same size of combustion explosion/bearing wear per rev/whatever, and same rate of work done, as running the 2200 hp version (same engine) at 90% load, which all of a sudden doesn't look so clever if this is the religion you believe in.

So if you run the 2200, 2400, 2600hp versions all at 75% load, the bigger engines will wear out faster AOTBE because, if you don't allow yourself to be duped by dashboard load % readouts, you will see that the bigger engines have (in truth) a higher loading than the 2200hp version. Seen through the eyes of the internal components of the 2200hp engine, the 2600hp engine's load% is about 90%, even though its dashboard says 75%. The 2600hp boat's dashboard only reads "75%" because the denominator has been played with. Don't be fooled (or, in your case, try becoming unfooled).

I was “ @ MapishM “ in case you missed that ? Shooting the breeze with 700 / 800 Hp fuel burn boats .Of which he tossed in his figures , being from larger 15 L V 8 s in a larger boat less relevant than mine I offered up .But still worthy of interest Imho .

Less rpm means greater longevity.Pretty simple really .

. Your 2600 Hp taking only 2000 Hp will run at lower rpms than the 2200 hp taking the same 2000 Hp .So will wear less AOTBE.

If you match the motors to the boat whereby you can achieve your speed without revving the nuts off them in commercial environment like the sport fisher guys they report they last longer suggesting the 80 % load rule . As I said folks can take the 80 % load rule as they wish .

Having said that in the leisure world the likes of MapishM, DAW , J Rudge , OP John , and indeed myself arn’t racking up multiples of 1000 s hr / annum with our 12-15 L engines .Nor do our livelihoods depend on a working boat . We have in common lost the warm blanket of new engine warranties and are now arguably running aged engines .Fuel consumption aside imho more than just a passing thought needs to be applied to sympathetic running / longevity .Running @ high than necessary loads at higher rpms unsympathetically is courting big bills .



In terms of the proposed del trip , back on topic
Confidence level ?
It’s up to John to set the rpm s ( which reflects on load directly) I wouldn’t personally with that new boat to me blast off at 2000 / 2100 rpm to achieve 25 knots from picking up the keys with the contract ink still wet . I am sure this will split opinion on here .

On my del trip Naples / Cannes iirc 600 nm we cruised 1650 rpm 25/26 knots with a pair of new to me 12.8 L motors .
Overcautious - hands up to that ? Just made sense to keep the load down FWIW around 70 % .

 

[jfm]

You still can't understand that the load %'s you quote are as much a function of the random denominator as they are a function of the non random numerator. Therefore they are meaningless values. You're worshipping a false god, and can't see it. Anyways, no worries - I'm seeking only to point out the meaninglessness of load percentages so that those who do understand the physics are reminded of it. You carry on with your 80% or 70%, and your belief that it's a sweet number because it's comfortably less than 100%, conveniently forgetting where the denominator came from .

Folks can take the 80% load however they wish, if they are happy to believe in garbage. But folks who understand the engineering won't take is as they wish - they will take it for what it is, which means recognising that the denominator in the 80% calculation is an entirely man-made number not rooted in any fundamental properties of the engine, and so they will correctly take the 80% "rule" with a pinch of salt.

As a matter of engineering, your 3rd para is incorrect but I'm not going to go down the rabbit hole of debating that with you.

 

[Portofino]

Two separate franchised MAN engineers an Italian and French , seem to concur with the 80 % mantra . From conversations with them .

Esp as the season progresses and fouling starts to take it toll .Better not to get into overload scenarios by checking in on the load values and setting cruise on those . What’s not to like doing this btw ?
[As far as the Ops concerned his boats fresh + clean ]

Generally most stuff that drifts across from the Atlantic is as you infer is crap , but occasionally a tiny bit is of good info finds it’s way to EU shores .Those American sport fishers from there experience with this 80 % load thingy have a point imho .For those unfamiliar with this ……the best fishing grounds are often miles away from the dock .So speed often 4 hrs + is important to get to and from where the bigger fish feed .Hence the engines get a daily pasting x2 , and rack up hrs .The actual trolling time is tiny .They apply this 80 % mantra across the who spectrum , Cat, Cummins,MAN , MTU etc


Any one that’s been around ICE in all there irritation’s , be racing cars , bikes , marine diesels , 2 T / 4 T or what ever know lower rpms extends life .Or turned around continually working the higher rpm range’s shortens life .Certainly increases risks of failure .

Busting a garden strimmer is different to busting a 12 L upwards marine diesels .Different financial consequences.

If you think it’s ok to spend loadsa time with bigger ( jugs in excess of 2 L each ) marine diesels running between 80-100 % load then fine , particularly aged engine’s unknown to you then fine .

You said it yourself in your SL new build thread speccing bigger engines to run at a lower rpm , ok slight more for refinement NVH , but a pair of 2400 Hp s will achieve cruising speed at lower rpms than the stock lower Hp AOTBE .
They will the internals ultimately wear out less than the smaller higher rpm motors .
You might even depending on the props , g boxes ( ie AOT not being E ) lower the fuel consumption.Win win for you .

 

[Portofino]

As a matter of engineering, your 3rd para is incorrect but I'm not going to go down the rabbit hole of debating that with you.

This one ?
[Your 2600 Hp taking only 2000 Hp will run at lower rpms than the 2200 hp taking the same 2000 Hp .So will wear less AOTBE.]

But you are agreeing with me here , taken from your SL thread .

 

[MapisM]

Those sports fisher guys are usually talking garbage, as is very common on US forums.

ROTFL, and don't get them started on deep vee hulls and Carolina flare!
Christ, most folks over the Pond are even genuinely convinced that their crappy 120V/60Hz components are the best in the world...!

 

[MapisM]

@ MapishM We are all agreeing with Johns calcs / assessment .Just arriving from different destinations.It healthy it’s called convergence.
....

Don't overcomplicate simple stuff, I was only arguing about your statement "speed is irrelevant", nothing else.
If I run the engines all day long while docked, at idle and with no gear engaged, my fuel burn in lph is unbelievably low...!

 

[Portofino]

Don't overcomplicate simple stuff, I was only arguing about your statement "speed is irrelevant", nothing else.
If I run the engines all day long while docked, at idle and with no gear engaged, my fuel burn in lph is unbelievably low...!

Talking cruising .Silly statement ^

 

[MapisM]

Talking cruising .Silly statement ^

What else would you expect, in a forum?
Silly members, silly statements!

PS: aside from this sad fact of life all of us must live with, you might also be interested to check out this webpage.

 

[Martxer]

This one ?
[Your 2600 Hp taking only 2000 Hp will run at lower rpms than the 2200 hp taking the same 2000 Hp .So will wear less AOTBE.]

But you are agreeing with me here , taken from your SL thread .
View attachment 160300

even I understand what Jmf is on about and know nothing about physics.

 

[jfm]

Two separate franchised MAN engineers an Italian and French , seem to concur with the 80 % mantra . From conversations with them .

Esp as the season progresses and fouling starts to take it toll .Better not to get into overload scenarios by checking in on the load values and setting cruise on those . What’s not to like doing this btw ?
[As far as the Ops concerned his boats fresh + clean ]

Generally most stuff that drifts across from the Atlantic is as you infer is crap , but occasionally a tiny bit is of good info finds it’s way to EU shores .Those American sport fishers from there experience with this 80 % load thingy have a point imho .For those unfamiliar with this ……the best fishing grounds are often miles away from the dock .So speed often 4 hrs + is important to get to and from where the bigger fish feed .Hence the engines get a daily pasting x2 , and rack up hrs .The actual trolling time is tiny .They apply this 80 % mantra across the who spectrum , Cat, Cummins,MAN , MTU etc


Any one that’s been around ICE in all there irritation’s , be racing cars , bikes , marine diesels , 2 T / 4 T or what ever know lower rpms extends life .Or turned around continually working the higher rpm range’s shortens life .Certainly increases risks of failure .

Busting a garden strimmer is different to busting a 12 L upwards marine diesels .Different financial consequences.

If you think it’s ok to spend loadsa time with bigger ( jugs in excess of 2 L each ) marine diesels running between 80-100 % load then fine , particularly aged engine’s unknown to you then fine .

You said it yourself in your SL new build thread speccing bigger engines to run at a lower rpm , ok slight more for refinement NVH , but a pair of 2400 Hp s will achieve cruising speed at lower rpms than the stock lower Hp AOTBE .
They will the internals ultimately wear out less than the smaller higher rpm motors .
You might even depending on the props , g boxes ( ie AOT not being E ) lower the fuel consumption.Win win for you .

Mechanics, not engineers.
Just because someone says something, doesn't make it correct.
You're never going to settle a debate with knowledgeable people by arguing "Well my mechanic said so".

 

[jfm]

This one ?
[Your 2600 Hp taking only 2000 Hp will run at lower rpms than the 2200 hp taking the same 2000 Hp .So will wear less AOTBE.]

But you are agreeing with me here , taken from your SL thread .
View attachment 160300

The part I was (obviously) disagreeing with was the "So it will wear less". Yet again, you post some evidence in support of your argument (in this case a post I wrote in the SL thread) without realising the evidence is working against your argument not in support of it.

All I said was the bigger-rated engine will do lower RPM, aotbe, which is obvious, but that is not saying it will wear less. Wear and RPM are different things; explosion magnitude (inside the cylinder when the firing happens) has lots to do with wear. You've even highlighted the bit where I talked about size of bangs inside cylinders.

Last time you posted evidence that hurt your case, I suggested you check which way the gun is pointing before you pull the trigger. Now I can see that you don't know anything about guns, and don't know which end the bullet even comes out of. You just post things that relate to the debate, wishful-thinkingly hoping they support your argument but having any clue whether they do or not. I need to give up! Enjoy your 80% load setting (without having any clue what that 80% is 80% of) and let's not worry about any of this

 

[Portofino]

The part I was (obviously) disagreeing with was the "So it will wear less". Yet again, you post some evidence in support of your argument (in this case a post I wrote in the SL thread) without realising the evidence is working against your argument not in support of it.

All I said was the bigger-rated engine will do lower RPM, aotbe, which is obvious, but that is not saying it will wear less. Wear and RPM are different things; explosion magnitude (inside the cylinder when the firing happens) has lots to do with wear. You've even highlighted the bit where I talked about size of bangs inside cylinders.

Last time you posted evidence that hurt your case, I suggested you check which way the gun is pointing before you pull the trigger. Now I can see that you don't know anything about guns, and don't know which end the bullet even comes out of. You just post things that relate to the debate, wishful-thinkingly hoping they support your argument but having any clue whether they do or not. I need to give up! Enjoy your 80% load setting (without having any clue what that 80% is 80% of) and let's not worry about any of this

There are less “bangs “@ lower rpms , you said it yourself .It obvious it’s crank bearings or any other spinning / moving part will wear less at the lower rpms AOTBE .

loads is a representation of the amount of fuel burnt .CAT life overhauls on fuel vol burnt .So it follows the lower load run ( if you can ) assuming all temps are within specs ie 75 % vs a engine running at say 95 % the lower loaded will last longer .

It ain’t my 80 % rule btw thought I made that clear .

Interesting when I catch you out for want of a better term , more like question what you say politely you seem to follow a pattern of three themes .
1- talk about physics , Engineering etc as if we the readers don’t understand , try and baffle us somehow without actual any real explanation
2 - Drop in it’s not worth telling us , hiding behind haven’t got time …….which is a cop out .
3- Start going for the man not the ball when I really expose you .

Feels like school bully behaviour if i am honest John .

Theres absolutely nothing wrong setting cruise using load guys .Setting cruising speed isn’t limited to this btw .
Overloading shortens marine Diesel engine life

As far as evidence for this ^^ folks go hunt down your own ,
Just one here ,
Diesel Engine Overload: Diesel RPM Too Low?

There‘s nothing more I can add that’s not been written ^ .
Wish the Op a successful del trip and the engines are treated with sympathy.

 

[jfm]

Portofino we have done this to death. As I said, you rock on using your 80%, not questioning what it is 80% of. I'll use item #2 please and happily leave this debate, for want of time and energy.

 

[SC35]

There are less “bangs “@ lower rpms , you said it yourself .It obvious it’s crank bearings or any other spinning / moving part will wear less at the lower rpms AOTBE .

My A-Level Physics is telling me this is entirely incorrect.
The assumption is that the engines at various power outputs are mechanically identical, apart from ECU mapping.

In which case ... the higher output engines at the same RPM will have higher prop pitch, greater forces applied to bearings, bigger bangs inside the cylinder, higher EGT.
In most cases, this is not an issue either way because the components inside the engines will have been specced to have a reasonable lifetime with the uprated output.
But the margins for overloading due to less than perfect props or fouling might be smaller with the higher output engines.

Marine Engines take a long time to "wear out" and are more likely to fail because something arbitrary has broken.

 

[Portofino]

My A-Level Physics is telling me this is entirely incorrect.
The assumption is that the engines at various power outputs are mechanically identical, apart from ECU mapping.

In which case ... the higher output engines at the same RPM will have higher prop pitch, greater forces applied to bearings, bigger bangs inside the cylinder, higher EGT.
In most cases, this is not an issue either way because the components inside the engines will have been specced to have a reasonable lifetime with the uprated output.
But the margins for overloading due to less than perfect props or fouling might be smaller with the higher output engines.

And go faster , you forgot to mention .This is because you have for some reason you are in effect comparing apples / pears .
We are talking about the same boat speed , so the larger Hp due to its availability to swing a bigger pitch prop , ( you got that but right ) will run at a lower rpm for the same speed and lower load .

So why did you say ^ “ same rpm “ ?? Eh ?

Load is the % fuel used .What’s demanded and actually burnt over what’s available at rated WOT .Could be measured in vol by sensors or more likely with electronic injectors the opening time , either way you end up with a % .
As post #22 JFM pointed out .

Because the bigger hp motor lower denominator is greater , more Hp 2600 ,and the 2400 Hp , more fuels pulsed in the cylinders than the 2200 Hp version for the same boat speed its load will be lower .Or turned around at the same load move faster due the bigger prop pitch .

You guys are moving the goal posts . As I illustrated sowing JFM s screen shot of his new build .= he said “ bigger engines will run - 100 rpm lower at any given cruising speed “
Lower running rpms over the years = lower wear n tear .
I am not disagreeing with what you are saying .Just pointing out like I did with JFM at the same boat speed it’s lower rpms .
It well documented the further up the Hp tree you go with the same block , the more you stretch it Hp wise given the internal components and more or less identical it shortens longevity .Took that as read . What point are you making btw in the context of this del trip ?

Back to the op who obviously can’t suddenly re spec his D12 s , re map it etc like you and JFM are talking about .
He can’t increase the denominator it’s fixed .
But he can change the top figure by dropping the revs moving the load down .
As Steve Dashew suggested in the link I gave …l.with the proviso the temps / pressures stay in specs .

All I said bearing in mind it’s new to him from personal experience on a del trip run at the lower rpm s lower load ( it’s had a fresh AF so that drops fouling out ) ,Take the 1900 rpm 23 knots on its first 200 miler . Cautious me !We still don’t know the rpm for the 25 knot suggest cruise .Load isn’t rpm , throttle position btw , but it’s all we have in this example and as I said the hull fouling is taken out of deliberations …..for now !The op hasn’t given any fuel burn rates from the sea trial .

When he gets it to its home berth he can play around with the cruise speed , the cylinder bangs .
look at his fuel burn rates as the seasons fouling progress and cruising crap/ stores accumulates .

Here better said by this guy .
https://www.outerreefyachts.com/docs/How-Long-Will-My-Engine-Last-PassageMaker.pdf

 

[MapisM]

You guys are moving the goal posts

R U for real, PF? I just cross-read the last posts (to avoid losing the will to live), and if there were a quiz asking to tell in three words what your point is, my honest answer would be IDK.

 

[Portofino]

R U for real, PF? I just cross-read the last posts (to avoid losing the will to live), and if there were a quiz asking to tell in three words what your point is, my honest answer would be IDK.

Does a pic work better for you re my “ moving goal posts “ ? .
Can you see it .

 

[Portofino]

Remember guys the longer lasting lower rated commercial engines of the same block run at LOWER rpms .