MAN Engines

[menta]

Dear group,
Do you know where I could find a comparison or test/tests (ideally from an independent source) of the MAN V8 1200 HP and the MAN V12 1400HP?
Does anyone have personal experience with either of these engines?
I have always been a CAT guy, but unfortunately today CAT's are not offered that much with European boat builders.
Probably due to foreign exchange considerations...
Thank you
Menta

 

[Portofino]

No personal experience of the modals mentioned but they are modular and I have been running 1/2 of a V12 in the 12 L straight 6 format for the past 4 seasons .Annual services .
It’s been a trouble free time ,on the button every trip .

I will add the caveat if I may , of not overloading them .Overloading applies to any marine diesel .So this now brings us round to the install - kg,s ,drag , anticipated cruise speed ......!

For me I tend to run / plane below or at 80 % load .Realise others don,t know or care .
So the longevity or breakdown hassle , repair bills can be more iatrogenic than marque specific .

In simple En it’s depends what they are in and how they are used

In your deliberations go for the biggest most powerful engines in the lightest boat choice .
My 0.02 p worth

You may find this illuminating?

https://www.thehulltruth.com/boatin...rtfish-builders-love-man-engines-so-much.html

 

[volvopaul]

When MAN threads come up I instantly thing about Latestarters comment once on the subject. Mangrenades !

 

[MapisM]

I have always been a CAT guy, but unfortunately today CAT's are not offered that much with European boat builders.

Agreed, that's a pity, particularly when you think that 1400hp is Cat C32 territory - an engine which puts anything from MAN to shame.

Anyway, between the two engines you mentioned, if the boat needs that level of power, I'd rather have the V12 than the V8, in principle.
In fact, the former has exactly 50% more displacement than the latter, and their respective higher power models currently available are 1900 and 1300hp (i.e. 50% more displacement, 46% more power).
Now, the V12/1400 is 26% less powerful than the 1900, while the V8/1200 is only 8% less powerful than the 1300.
In other words, the former is bound to be less stressed than the latter.

Btw, it's worth mentioning that the higher power which MAN used to squeeze from those blocks was 800 and 1100 hp, respectively for the V8 and V12, before the advent of electronic tricks. This gives you an idea of how stressed these blocks are, nowadays... :ambivalence:

 

[[2068]]

But how many engine failures are actually caused by an over stressed block?
Compared to an intercooler, turbo, or other cooling system or lubrication failure?

 

[MapisM]

But how many engine failures are actually caused by an over stressed block?
Compared to an intercooler, turbo, or other cooling system or lubrication failure?

Well, when you are squeezing more ponies out of the same block, also the cooling and lubrication systems must work harder, I reckon.

Btw, the output of the heavy duty versions of those very same V8 and V12 blocks are still "only" 680 and 1000hp, respectively.
Which is exactly the same output that the second to last mechanical versions used to have.
Funny coincidence, 'innit…?

 

[Portofino]

Well, when you are squeezing more ponies out of the same block, also the cooling and lubrication systems must work harder, I reckon.

Btw, the output of the heavy duty versions of those very same V8 and V12 blocks are still "only" 680 and 1000hp, respectively.


Which is exactly the same output that the second to last mechanical versions used to have.
Funny coincidence, 'innit…?

Not really
Multiply the cubic inch displacement (CID ) by 1 , that’s where the Hp should be or lower for super longevity.
Assuming regular timely services etc .

Here’s an extract from a marine engineer re longevity

[Diesel engines are capable of having a long life when the power to displacement ratio is low. But when they start jacking up the power, beyond what the manufacturer originally intended, that benefit disappears. There is a very simple formula you can apply to estimate service life: simply multiply the cubic inch displacement of the engine times one. The result is the maximum amount of horse power you can have and still expect a reasonable service life. A 6V92 engine is 552 CID; at powers greater than 550, these engines don't last. At 450, they'll go 10 - 15 years easily.
We recently surveyed a yacht with a pair of 8V71N (naturally aspirated) Detroit Diesels rated at 325 hp that hadn't been overhauled since new 1981. Now, an 8V71 has a 568 cubic inch displacement; the fact that these engines have a 0.56:1 power/displacement ratio explains why they could run so long.
Conversely, divide the CID by the horse power, and the greater the result UNDER the factor of one (1), the longer engine life you can expect. If you have an engine with an 0.70 CID/HP ratio, then you can expect 3000 hours engine life. Otherwise, you are a victim of the myth. ]

Aside we are drifting into a place that you can’t stop the forever rise of Hp from internal combustion engines .
Honda,s S2000 engine with the 2 L block was somewhere between 237/250 Hp at launch way back at the turn of the century.
Alloy block ( I,ll return to that later ) .At the time there was great t sucking of teeth as this Hp is north of 3 L territory.
To date going on for 1 M blocks ,in outboard too there’s not a single example worldwide of a busted engine ,not one .

Clue is the fibre reinforced block .Its alloy with fibres to reinforce. valve gear too all quads stood up ,but they Honda know a thing about multivalve tech from the 70 ,s bike engine days .
Returning to marine diesels .
Take the CAT C32 the 1900 ACERT variant is a different block albeit same size to fit the modular liners / heads / valve gear etc than the 1652 Hp version of the C32 .

So it’s unfair to suggest , like the nersay doers did with the S2000 engine that it’s gonna get all stressed out or what ever .
As you infer with marine diesels there’s been huge jumps in electronic control especially the fuel management.
Behind the scenes block tech has kept up in step too .

As I said with boats runing large displacement engines it really boils down to how they are used re overloading episodes .
Running @1750:rpm all day or 2150 rpm , you takes your pic .

The mangrenade thing was almost 20 y ago now I think a batch of faulty injectors from Bosch melted a few pistons I understand mostly in the V10 series .
All the pins pulled years ago .
That’s not to say A N other manufacturer will have a repeat faulty injector episode , think of the automotive VAG com group with there ignition coil pack debarcle in there petrols a decade ago .
Retiring to boats CAT went through a recent debacle leading to class action in the states regarding intercooler corrosion , a 3 p part leading to hydro lock and bent rods mostly with the C32 you infer above .
Re visit the link I posted #2

So they all have dropped a 8*llock of two with outsourcing parts .

If you are buying new or nearly new like the OP he can,t turn the clock back or ask for a heavy duty cycle in a liesure boat .
As said today MAN are made wholly in Germany by German engineers and I think that still holds gravitas re reliability.

Aside buying used CAT rely on zincs scattered about in the cooling system ,where as MAN use a comman earth type external hull anode which is easy to access and see and deal with ,less prone to forgetfulness.

 

[MapisM]

Porto, sometimes (well, rather often, if I'm honest) I struggle to follow your train of thought.
You start quoting "an extract from a marine engineer re longevity" which essentially confirms my previous argument, and then jump to the Honda S2000 engine - what the heck?!

Btw, funnily the "longevity ratio" that you mentioned is as follows, considering the current higher power versions of the engines mentioned so far:
MAN V8/1300: 1.32
MAN V12/1900: 1.29
CAT C32/1900: 0.97
So, it seems to me that you could have saved yourself the time to write a long post to comment mine, by simply replying "I agree"...

Regardless, back to the OP point, I was simply suggesting that between the V8/1200 and the V12/1400 I'd rather go for the latter (whose
"magic ratios" are in fact 1.21 and 0.95 respectively, for the records...), nothing else.

If I would have thought that MAN only builds disposable engines, I wouldn't have bought a MAN powered boat.
BUT, would I have rather chosen (in the same power node) the Cat 3406, if given the choice? You bet.

 

[Portofino]

No worries P
Illustrating how the old school equation of CID x1 for longevity Hp has been eclipsed by modern block tech .
Flowerpower alluded to earlier if I understood his post re questioning engine failure in marine diesels due to blocks .
Actually there is an example dear to many hearts on here re blocks
D12
The oil pan leaks are i believe due to inadequate webbing strength at the bottom of the crank case .
This causes a twist in the block and breaks the pan gasket seals in the 715 Hp upwards variants .

As you say we are N of 1 now in the CID x Hp ratio and there’s only one Dir it’s gonna go .
Just a matter of time before it’s x2 for liesure boats .

 

[jfm]

All these are isolated examples only findable because of the internet. 99.99% of D12 do not exhibit that. I have 1000+ hours of 4x d12 ownership 715/775 hp with no problems. Ditto 4x cat32. And I've only ever had 2 friends (one being TCM of this forum) who have had major work (head off) in their 1200/1360hp MAN v12s at <500 hrs. So these are isolated incidents and you can't automatically extrapolate and say these engine types will generally show these faults.

 

[MrB]

I noticed Sunseeker had started to spec the new MAN engines over the MTU's, more power but smaller. Two SS86's for sale with 1000H in their first year. (with MAN engines)

 

[MapisM]

As you say we are N of 1 now in the CID x Hp ratio and there’s only one Dir it’s gonna go .
Just a matter of time before it’s x2 for liesure boats .

Well, who knows?
Otoh, the HP/CID ratio of the FPT engine heavily prepared by Buzzi for his (successful) attempt to improve his own world speed record for diesel powered boats is 1.75, and nobody in his right mind would use that beast for anything else than a racing boat.
My guess is that we will not see x2 engines in this life, aside maybe from the teenagers among us - if any...

 

[Boat2016]

But how many engine failures are actually caused by an over stressed block?
Compared to an intercooler, turbo, or other cooling system or lubrication failure?

Probably very few, just looked up CID & HP of a few and most of the smaller marine diesels are going to fail in a big way if we believe the theory mentioned above, what are we going to do ? Panic or keep on boating, I know what I will do. What evidence is there to back up this theory ?

 

[volvopaul]

Most high performance marine diesels fail from either poor maintenance both in the oil and fuel dept and high piston temp due to partially blocked intercoolers .
The fuel side is down to dirty fuel not lubricating the pump and injector nozzle , the oil side down to oil that’s past it’s useable hours .
The intercooler issue is t so much on edc controlled or common rail engines because they are governed by coolant temp, load relative to throttle position and air inlet temp .
It’s the older mechanical engines that fail when the owner sits there cruising with the throttle flat out , cloud of black smoke behind them pouring fuel into a cylinder that can’t burn it due to lack of good cool airflow .
Another factor is high piston temp due to clogged up piston cooling jets, more turbo diesels have them , and if they fail the piston overheats and breaks up.

The early v8 mans were renown for it , I nearly bought a sunseeker very cheap with one blown piston some years back , to be fair the parts prices were very fair at the time as they were truck parts prices , the main issue was extraction of the engine to get at it , massive heavy lump.

 

[MapisM]

The early v8 mans were renown for it , I nearly bought a sunseeker very cheap with one blown piston some years back

Do you possibly remember the version/year, P?
I suppose you are talking of mechanical engines, whose V8 block used to have a 680hp output up to the mid 90s, when it was raised to 800hp, which they sold as hot cakes to many yards, till they eventually introduced the 900hp common rail (in 2004, IIRC - with a fair share of troubles in the first years of production...).

 

[volvopaul]

It’ was the 680

 

[PowerYachtBlog]

Do you possibly remember the version/year, P?
I suppose you are talking of mechanical engines, whose V8 block used to have a 680hp output up to the mid 90s, when it was raised to 800hp, which they sold as hot cakes to many yards, till they eventually introduced the 900hp common rail (in 2004, IIRC - with a fair share of troubles in the first years of production...).

The 820hp V8 version of this introduced in early nineties was deemed a very good performing engine and also very reliable. It had the habit of smoking when started cold for quite an amount of time.
Yes many Italian yards sold it as hot cake. From short of 50 feet up to about 60 feet.

 

[MapisM]

It’ was the 680

Good to know, thanks.
I was sort of hoping to hear that, 'cause I've got a couple of V8/800 in my boat (the very latest ones, built just before they introduced the 900CR), and based on my searches before buying the boat, they had a pretty decent reputation.

 

[MapisM]

The 820hp V8 version of this introduced in early nineties was deemed a very good performing engine and also very reliable. It had the habit of smoking when started cold for quite an amount of time.
Yes many Italian yards sold it as hot cake. From short of 50 feet up to about 60 feet.

Careful there, W.
In the early 90s, MAN did have an 820hp engine in their range, but it was the V10. Back then, the V8 was only available with a 680hp output.
I don't know exactly when the V8 was upped to 800hp (it was definitely 800 and not 820, btw), but it was in the mid/late 90s, anyway.

Otoh, it's true that the last mechanical V10 (820hp) was widely recognized as a solid engine, even if as you say very smokey on cold start.
It's when they introduced electronic control, that the V10 reliability began going downhill (particularly with the non-CR 1050hp first, but also with the CR 1100hp afterwards), till they eventually phased out the V10 block altogether.
Fwiw, I tried the V10/1100 on a F590, and I wasn't impressed at all: nowhere near as smooth as the V12, and also worse than my mechanical V8, even if they are also far from the V12 smoothness, at low rpm.

 

[Deleted User YDKXO]

For reasons I have never understood the MAN V12 engines get a bad press on here. All I can say is that I own a 12yr old Ferretti 630 with MAN V12/1200hp engines which have run faultlessly for around 400hrs in my possession and now show around 1100hrs in total. They had a full diagnostic test under load this year carried out by a MAN technician and got a completely clean bill of health. I have owned quite a large number of boats over the years with various manufacturer's engines and I can honestly say that the MAN V12 engines are some of the best I've run. They're smooth, quiet (at least in my boat) and have bags of low down torque which means that even a big heavy lump of a boat like mine accelerates very well to a top speed of 34kts

The only downside I have found is that the MAN servicing schedule requires that the intercoolers are removed and cleaned every 2yrs but otherwise servicing costs are reasonable compared to other brands

I have also had very good experience with Cat engines so I can say nothing against them

With regard to the MAN V8/1200hp engines I have no experience but personally I'd much rather have the V12 engines which I would bet have more torque and are smoother