Fleming 58 video

[MapisM]

Sorry MapishM— forgot size of your engines ?

LOL, no worries, you actually missed Deleted User's engines size as well, since they are 22 rather than 24L...
183 is the magic number, when it comes to Mercedes-derived V engines.
In fact, before replacing it with their 2 liters/cylinder series, MTU called that block (which is exactly the same used by MAN) "183 series" - which stands for 1.83 liters/cylinder.
So, V8/10/12 are 1.83*8/10/12 respectively.
Mind, your engines do NOT follow the same rule, because in the 6L the bore is the same, but the stroke is longer.

Back to the point, unfortunately I have no idea about the fuel burn of my engines below 1000rpm, which is the first "step" reported in actual tests - and which pushes the boat at 9.5kts, burning 42lph.
But since 9.5kts is already a fair bit above D speed, I would expect the 42lph to at least halve, when running at tickover rpm, which is good for 6 kts or so.
In fact, I'd be happy to bet that also TH's Nordie burns fuel like there's no tomorrow at 9kts, with a HUGE difference compared to her normal 10 lph @ 7kts.
I will soon stay in the US for a couple of months, and I might decide to burn some bucks into Floscan gauges, if available at decent prices... And if I will, after installing them I'll be able to update with some true numbers! :encouragement:

 

[Deleted User YDKXO]

MikesF,s v 12 - 24 L ........your 32 L , and even my 12 L cannot get any where near 10 L / h cruising about in the sun .

Portofino, actually my engines are MAN V12s capacity 22l each. They are electronically controlled so there is a fuel consumption readout in lph on the engine helm displays. Shortly after buying my boat I noted fuel consumptions at various rpm for both engines and related them to GPS speed. At 7.2 kts, the engines were consuming 8lph each which translates to around 2nmpg. I have to say that this does drop very quickly. For example at 10.8kts the engines are consuming 32lph each which translates to 0.77nmpg.

The moral of the story is that if you want to save fuel go as slowly as you can ie minimum in gear speed. Actually I have tested my boat on one engine only and she does 5.2kts which equates to nearly 3nmpg but I never run on one engine only for extended periods for fear of damaging the other gearbox

 

[MapisM]

Shortly after buying my boat I noted fuel consumptions at various rpm for both engines and related them to GPS speed.

M, did you possibly do the same with the Cat 3196 that you had in your F53?
If yes, I'd be curious to hear what sort of numbers you got, through the whole range.
Actually, Ferretti did not install on the 53 the Cat displays similar to the MMDS that you've got now, but I think that you could still get load, fuel burn etc. as "rotating" numbers on the small LCD display embedded in one of the gauges...

 

[Deleted User YDKXO]

M, did you possibly do the same with the Cat 3196 that you had in your F53?
If yes, I'd be curious to hear what sort of numbers you got, through the whole range.
Actually, Ferretti did not install on the 53 the Cat displays similar to the MMDS that you've got now, but I think that you could still get load, fuel burn etc. as "rotating" numbers on the small LCD display embedded in one of the gauges...

Yup youre right. The lph numbers were available by scrolling through the guages.

This is the graph that I constructed using those numbers

Btw just for the record the trim tabs were adjusted to optimise speed for every point on the graph, the test was carried out in flat calm conditions and at the beginning of the season so these are best case numbers

 

[Portofino]

Portofino, actually my engines are MAN V12s capacity 22l each. They are electronically controlled so there is a fuel consumption readout in lph on the engine helm displays. Shortly after buying my boat I noted fuel consumptions at various rpm for both engines and related them to GPS speed. At 7.2 kts, the engines were consuming 8lph each which translates to around 2nmpg. I have to say that this does drop very quickly. For example at 10.8kts the engines are consuming 32lph each which translates to 0.77nmpg.

The moral of the story is that if you want to save fuel go as slowly as you can ie minimum in gear speed. Actually I have tested my boat on one engine only and she does 5.2kts which equates to nearly 3nmpg but I never run on one engine only for extended periods for fear of damaging the other gearbox

I,am for me approx 1/2 size ( just over a bit ) for me - sure tick over in Neutral -it’s 3 L / H r , comparable to your 8 ?, but as soon as I engage Fwds. 1 st click and the prop turns then it’s 15 l / hr , same rpm .
I can’t do 6 knots , it’s impossible with both engines * tick over is over 7 .+
If we all go off for a day,s boating it’s does not really matter if TH is doing 6 , somebody else me @ 825 rpm is over 9 ,or any others somewhere inbeween , in fact I,d be surprised if JFM can do 6 tbo

Just leaving em @ tick over ( not wanting to reignite the low rpm / knackers them debate ) waaaaay too little load n heat
1000 rpm waaaay above Sensible D rpm , so that leaves a bit more rpm above tickover for me another 125 .adding up to 825 , Which for Nav is man maths 10 miles an hour .

TH mentioned “ nobody has mentioned fuel costs “ or words to that effect
Then it seems to me the guys with bigger planning boats chimed in and switched it round to range .
Fine , but TH ,s set up will burn less.Ok he will arrive last ,but in a 3-4 hrs run , by the time we have anchored , phaffed a bit ,got a few water toys out etc , he’ll be popping into the bay ,He won’t miss Lunch ,just one of use will have get the prawns on

Sorry Deleted User , I just can’t see your 8 L / hr with fwd engaged at a none tick over say 800 or what ever , or even 1 st click @
Tickover

* agree can,t be arsed turning bolts on the g box to windmill for any length of time .Cost of a engine / box removal to fix exceeds any 2 nd engine fuel bill .-

 

[Deleted User YDKXO]

I
Sorry Deleted User , I just can’t see your 8 L / hr with fwd engaged at a none tick over say 800 or what ever , or even 1 st click @
Tickover
.-

PF I can assure that I can read my own engine instruments

 

[jfm]

I,am for me approx 1/2 size ( just over a bit ) for me - sure tick over in Neutral -it’s 3 L / H r , comparable to your 8 ?, but as soon as I engage Fwds. 1 st click and the prop turns then it’s 15 l / hr , same rpm .
I can’t do 6 knots , it’s impossible with both engines * tick over is over 7 .+
If we all go off for a day,s boating it’s does not really matter if TH is doing 6 , somebody else me @ 825 rpm is over 9 ,or any others somewhere inbeween , in fact I,d be surprised if JFM can do 6 tbo

Just leaving em @ tick over ( not wanting to reignite the low rpm / knackers them debate ) waaaaay too little load n heat
1000 rpm waaaay above Sensible D rpm , so that leaves a bit more rpm above tickover for me another 125 .adding up to 825 , Which for Nav is man maths 10 miles an hour .

TH mentioned “ nobody has mentioned fuel costs “ or words to that effect
Then it seems to me the guys with bigger planning boats chimed in and switched it round to range .
Fine , but TH ,s set up will burn less.Ok he will arrive last ,but in a 3-4 hrs run , by the time we have anchored , phaffed a bit ,got a few water toys out etc , he’ll be popping into the bay ,He won’t miss Lunch ,just one of use will have get the prawns on

Sorry Deleted User , I just can’t see your 8 L / hr with fwd engaged at a none tick over say 800 or what ever , or even 1 st click @
Tickover

* agree can,t be arsed turning bolts on the g box to windmill for any length of time .Cost of a engine / box removal to fix exceeds any 2 nd engine fuel bill .-

Porto, my idle is 600rpm which is 7ish knots but I have a slow idle switch (standard with Cat) that drops idle to 500ish rpm and 6 ish kts

 

[Deleted User YDKXO]

PF I can assure that I can read my own engine instruments

Btw the minimum in gear idle speed of my engines is also 600rpm

 

[MapisM]

Wow, that's a VERY interesting table indeed Deleted User, thanks a bunch.
It should be mandatory for boatbuilders to disclose those numbers for every model...!

A few Qs on them, if I may:
- do you possibly remember also the g/box ratio and the props characteristics?
- was 695rpm the minimum in-gear speed? That sounds a bit high...
- assuming that the trim tabs numbers are meant as 100%=fully lowered, there are two conditions which I find surprising, i.e. very low and very high speed. Common sense (and also what I experienced so far with the DP) suggest that at D speed the tabs position should be irrelevant, and at 30kts the boat should be, if anything, a tad faster with them fully raised...

 

[MapisM]

I have a slow idle switch (standard with Cat)

Just in case you would be tempted to use it for a somewhat extended time, I've seen a C15 (formerly 3406) powered fisherman equipped with g/box trolling valve, and the builder explained me that it was added because Cat highly recommended them to use low idle switch as little as possible - typically for maneuvering, if necessary.
Just reporting it as I heard it, strictly fwiw.

 

[Deleted User YDKXO]

Wow, that's a VERY interesting table indeed Deleted User, thanks a bunch.
It should be mandatory for boatbuilders to disclose those numbers for every model...!

A few Qs on them, if I may:
- do you possibly remember also the g/box ratio and the props characteristics?
- was 695rpm the minimum in-gear speed? That sounds a bit high...
- assuming that the trim tabs numbers are meant as 100%=fully lowered, there are two conditions which I find surprising, i.e. very low and very high speed. Common sense (and also what I experienced so far with the DP) suggest that at D speed the tabs position should be irrelevant, and at 30kts the boat should be, if anything, a tad faster with them fully raised...

I suspect the reason that boatbuilders dont publish these figures is that they can vary so much according to sea conditions, sea temp, load, fouling etc. For example in UK waters under the same conditions you would expect an improvement in fuel consumption simply because the sea temp is lower

To answer your questions

No, sorry dont know gearbox ratio or prop size

Yes 695rpm was the minimum in gear speed. Cat quote 700rpm minimum for that engine

Correct. 100% means fully down. First the reason I tend to go at D speed in all my boats with the tabs well down goes back many years to my old River Thames cruising days! I was told that any boat tends to track straighter at slow speed with the tabs down and thats what I have found on many boats I've owned although as my boats have got larger, any effect of having the tabs down at D speed has been less. Second at P speeds we've had this discussion before. Ferrettis just seem to need plenty of tab down at P speeds to achieve their max speed. I'm not going to get into a discussion about whether this is good or bad thing only to say that I'm perfectly happy with that. My current F630 does behave more conventionally in that at speeds above 25kts, the boat achieves its best speed without any tab. However in the case of my F46 and F53, they both needed plenty of tab to achieve their best speeds at all speeds. I think with my particular F53, it was exacerbated by the fact that the owner specified an additional 1000l fuel tank which was located well aft behind the engines and I tended to keep it full so there was always an extra tonne of fuel under the cockpit. Anyway the tab % represent approximately where the tabs needed to be on my F53 to get the best speeds except at D speeds where I only kept them down for reasons of tracking

 

[Portofino]

Mike with your CAT s The F 53 Maybe @ ultra low say a few hundred rpm the fuel monitoring is not as accurate as higher up where it’s optimised?
Here’s a screen shot of my 12.8 L — 6 cylinder full EDC etc
So I,am figuring your 22 L MAN,s will be near 40 each. That’s 80 odd. Compared to TH. s 10
MapishM ,s 35 so 70 odd . just can,t see where your 8 each comes from .
Anyhow as you say the slower one goes the less we use .
Perhaps with different g box ratios and prop pitches and indeed top end speed , the boats are all very different L / hr
So it’s erroneous for me to extrapolate from just 1 set of data - mine to yours ,JFM , and MapishM based on multiples of CC .A think that’s it the discrepancy?
https://imgur.com/gallery/ZSXza

 

[Deleted User YDKXO]

Here’s a screen shot of my 12.8 L — 6 cylinder full EDC etc
]

Yeah but your screenshot shows 935rpm which has got to be well above minimum in gear speed. As you can see from the figures I put up for my Cat engines, at that rpm they would be consuming around 14lph each.

I'm surprised by the 61% load figure in your screenshot. Normally you dont see that kind of figure until a boat is planing. That seems very high for a a relatively low rpm. I'm guessing at 935rpm your boat would be doing around 10-12kts ie hump speed at which for sure it would be consuming a relatively high quantity of fuel

 

[MapisM]

I'm surprised by the 61% load figure in your screenshot.

+1, but as you say it's probably down to being pushing a "wrong" speed for the hull length.
Possibly together with the somewhat lower efficiency of very deep V hulls, though the F53 which we are using as yardstick was IIRC the last high deadrise Ferretti, at 19 degrees.
Regardless, PF, it seems that low load at low speed shouldn't be an issue for you!

 

[burgundyben]

I've waited a very long time for someone to post a graph like that. What a fascinating insight into the boat, and, gives such a clear decision making ability.

Brilliant, right up my nerdy street.

 

[Deleted User YDKXO]

I've waited a very long time for someone to post a graph like that. What a fascinating insight into the boat, and, gives such a clear decision making ability.

Brilliant, right up my nerdy street.

Well if you like graphs (I do too!) here is another similar one for my current boat, Ferretti 630 with MAN V12 D2842 LE433 1200hp engines

 

[Bouba]

I find the fuel consumption gauge to be a mixed blessing. It sort of becomes hypnotic and it’s the only thing you watch

 

[Portofino]

+1, but as you say it's probably down to being pushing a "wrong" speed for the hull length.
Possibly together with the somewhat lower efficiency of very deep V hulls, though the F53 which we are using as yardstick was IIRC the last high deadrise Ferretti, at 19 degrees.
Regardless, PF, it seems that low load at low speed shouldn't be an issue for you!

Yups that’s a silly rpm for D in the ,equation of calc true D regarding,WL .As you say it’s creating a bow wave .
Agree great speed ( can,t remember ) for engine longevity- re over the magic 50 % load — if that part of the MAN manual on duty cycle is to be adhered to or even believed .:encouragement:

Off to the boat end of next wk , if time may do a Deleted User esq graph .

 

[Portofino]

Well if you like graphs (I do too!) here is another similar one for my current boat, Ferretti 630 with MAN V12 D2842 LE433 1200hp engines

Nice shape - flat bit is great. Means you can or may as well when planning — thinking of the engines stick em @ 1800 or just under 1780 .In other words no need to cane them .

Do yours has a cylinder shut down of one bank @ low rpm ?
I know they are CR and mine are just before CR became the norm ( EDC - era ) , so perhaps the squirt timing is not as miserly as yours lower down .

My general view of that graph ^^^ is its pretty dam good or the engines / G box / prop s ,and hull are well matched .

 

[Deleted User YDKXO]

Nice shape - flat bit is great. Means you can or may as well when planning — thinking of the engines stick em @ 1800 or just under 1780 .In other words no need to cane them .

Do yours has a cylinder shut down of one bank @ low rpm ?
I know they are CR and mine are just before CR became the norm ( EDC - era ) , so perhaps the squirt timing is not as miserly as yours lower down .

My general view of that graph ^^^ is its pretty dam good or the engines / G box / prop s ,and hull are well matched .

I dont know whether the relatively flat consumption curve over the range of planing speeds is typical only of Ferrettis or typical of all planing boats. I suspect the latter and yes it does mean that in the typical speed range for a planing boat, 15-25kts, you can choose a speed according to conditions not according to fuel consumption

No I dont believe that my engines shut down any cylinders at low rpm. Yup the MAN engines and the F630 hull are very well matched. The boat is relatively heavy at 39t but these engines have plenty of torque to overcome that and never feel stressed