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Old 01-07-2011, 09:09 AM   #21
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RE: Horsepower versus Displacement

Marin,About #1 YOU are wrong. "Iv'e said the engine probably can do it" I did say that.
Anyway if I repeat you'll repeat and that serves no purpose that is positive.
But I do need to make an adjustment to my position in that you are partially correct on several issues. My Mitsu is rated for 1 hr WOT but I wouldn't do that. I saw a Mitsu on Yacht World that had over 10000hrs on it and it didn't get there at WOT. But it could have at 80% load. Diesel engines in industry do it every day. If your Lehman engines are actually weak and can't haul the mail so be it and I'm glad I hav'nt got one. I looked at perhaps over 100 boats powered by Lehman's and I don't recall any repowers. And I don't think for a minute they were ALL baby'd. Most of the engines had 4 to 6000hrs TT or since MOH. Like most anything there's a sweet spot that works best. Engine rpm and load sweet spots are almost always a point of minimal vibration. Has nothing to do w what's good for the engine or where the most torque is developed or where the lowest fuel burn is experienced. I would run my Mitsu at 2500rpm most of the time if I felt like it and that is equivalent to 2100 on the Lehman. Maybe it would'nt last 15000hrs but it would probably last 10000hrs and there's basically no chance that's going to happen.
Ha Ha * * ...I just thought of somth'in * *... I repowered my Willy that had a perfectly good 4-107 Perkins so maybe you're right * * new things are good!
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Old 01-07-2011, 11:30 AM   #22
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Horsepower versus Displacement

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nomadwilly wrote:

Marin,
1.* If your Lehman engines are actually weak and can't haul the mail so be it and I'm glad I hav'nt got one.

2.* Ha Ha * * ...I just thought of somth'in * *... I repowered my Willy that had a perfectly good 4-107 Perkins so maybe you're right * * new things are good!

*
1. The Ford Dorset (base engine for the FL120) is indeed a weak engine when operated in the manner it was originally intended to be operated, as a "heavy" truck engine.* In that sort of service, pulling heavy loads up hills, keeping up with the increasing highway speeds of the late 1950s, etc. it could not "haul the mail."

However, as Ford discovered, the same engine did very well in stationary industrial service and then as a powerplant in relatively low-power, low-load applications like combines, farm tractors, and so on.* So in boat service, if operated conservatively (as opposed to the way Ford had hoped the engine would perform) it is a long-lived, reliable engine as thousands of boats have proven over several decades.

Based on the history of the engine I have read and what I have been told about the engine by people who dealt with them for decades in the US and the UK, you can't get in trouble with a Dorset (FL120) unless you operate it in the manner in which it was operated in Ford's trucks--- high loads, high rpm.* That's when the engine will eventually bite you and enrichen the mechanics at your diesel shop.

2.* A popular repower for Grand Banks that were built with the FL120 or FL135 is the 150hp N/A Lugger (I don't know the* model number).* The Lugger is very close in size to the Ford engine but is based on a modern diesel (John Deere I think) with high reliability, good efficiency, and enough power to let the boater run the GB's semi-planing hull at a faster speed without stressing the engine.* Should we ever decide to spend the money to re-power our boat, this is the engine we would use if it was still available.


-- Edited by Marin on Friday 7th of January 2011 12:32:56 PM
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Old 01-07-2011, 12:50 PM   #23
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RE: Horsepower versus Displacement

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DavidM wrote:

New can be better, but not necessarily for low speed trawler use. I'll give you an example.

The newish Yanmar 4JH4 HTE is a 2 liter turbocharged 110 hp engine. You might think that it would be a good engine to push a 20,000 lbs trawler to hull speed producing 60 hp. Maybe but it would be producing 30 hp per liter to do that. And you have the extra complexity of a turbo and intercooler.

Then look at the John Deere 4045D a newish 4.5 liter naturally aspirated engine. It has an M2 commercial rating. It would be a good choice for that 20,000 lb trawler as the 60 hp would only be 13 hp per liter.

Big iron beats sophisticated turbo charged in all respects for a displacement speed trawler in my book. Unfortunately there are really no new 6 liter and up normally aspirated engines. So if you want a new 30,000 lb trawler it will come with a turbocharged engine.

David
I was thinking more like 20,000 pounds would require 30HP and 30,000 lbs. would require 45 HP. Think you have several non turbo sub 2700 rpm choices that can produce 30 to 45 HP all day.

Ted

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Old 01-07-2011, 12:51 PM   #24
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RE: Horsepower versus Displacement

Marin,
They made the Lehman conversions for many years. If it was known (how could it not be) that they were weak then why did'nt Lehman get another engine to marineize?Luggers popular in GBs? Never seen one listed or otherwise. I saw one GB that had a Deere in it but you said that was original. If that GB36 w the 55 Yanmars was FG and on the west coast I'd have been on it * * ..prolly.
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Old 01-07-2011, 01:24 PM   #25
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Horsepower versus Displacement

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nomadwilly wrote:
1. They made the Lehman conversions for many years. If it was known (how could it not be) that they were weak then why did'nt Lehman get another engine to marineize?
2. Luggers popular in GBs? Never seen one listed or otherwise.
1.* They did.* It's called the FL135.* Also, by the time Lehman got around to marinizing the Ford Dorset into the FL120 it had been in industrial and agricultural service long enough to have built a good reputation in this service.* It was only used in trucks for a few years.* And as you said earlier, there weren't that many diesels around in the 60s that lent themselves to marininzations for smaller boats.******

2. Perhaps the people who own them don't want to sell them.* Who knows?* But Alaska Diesel-Electric aka Northern Lights/Lugger told us they have re-engined quite a few GBs, not just in this area but all over.* Woodies and glass boats both.* I don't know exactly how many "quite a few" is.* This came out in a discussion we had with them not long after we bought our own GB and were exploring the options to get rid of the two FL120s.

There are several people on the GB owners forum who have GBs that were re-engined with Luggers.* From the accounts I recall reading, it's an excellent conversion for a GB32 or GB36.* For what most GB buyers want today the 150 hp Lugger is too small for the GB42 although if one didn't want to go much faster than 9 or 10 knots a pair of them would work great.* The FL120 was the standard powerplant for the GB42 until they moved up to FL135s and then larger engines like Cats and whatnot.




-- Edited by Marin on Friday 7th of January 2011 02:31:56 PM
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Old 01-08-2011, 09:55 AM   #26
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RE: Horsepower versus Displacement

I notice the wood GBs are going for cheap. Seems strange people would invest large amounts of money in a boat that won't deliver at sale time. But that guy w the little Yanmars sold his. What would 2 new luggers installed cost?
" They did.* It's called the FL135." That's the same 380 cu in Ford as the 120 isn't It?
Also you don't see many 135s so they let a lot of lemons out the door before doing anything about the "problem".
Anything w a Lugger would be nice but in a yacht any other engine would do just as fine. I could have put a 40hp Lugger in Willy but as soon as I got a wiff of the price I was outta there. It was ridiculous! I do recall MER was advertising a near slip-in Deere for a Lehman replacement but I've not seen one of them either. I have seen a lot of Lehman rebuilds though. You say that's usually over heating? I wonder how many over heated Lehman's got that way from bad design or operator negligence. I'd vote on the latter.
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Old 01-08-2011, 12:23 PM   #27
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RE: Horsepower versus Displacement

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nomadwilly wrote:

1.* I notice the wood GBs are going for cheap.

2. What would 2 new luggers installed cost?

3. " They did.* It's called the FL135." That's the same 380 cu in Ford as the 120 isn't It?* Also you don't see many 135s so they let a lot of lemons out the door before doing anything about the "problem".

4. I wonder how many over heated Lehman's got that way from bad design or operator negligence. I'd vote on the latter.
1.* Wood anythings (other than Gar Woods, Hacker Crafts, and vintage Chris Craft runabouts) go for cheap.* GB woodies have always been pretty inexpensive.* For example, in 1998 when we bought our GB36, wood GB36s from the first half of 1973 were selling for perhaps $50k average.* Fiberglass GB36s from the second half of 1973 were selling for $80k to over $100k for a really, really nice one.

2.* I don't know these days.* At the time we were considering it the total cost would have been about $40k.* But you're right--- unless the original engines have failed, a repower just to repower is often not at all cost-effective. On a boat like ours, the cost of a repower would never even come close to being realized in the resale value.* One does it for one's own satisfaction, not because it makes economic sense.* Like putting a $20k paint job on a boat that's worth $50k at best, which I've seen happen.* It was important to the owner to do this.* The cost logic was not a factor.

3.* The FL120 and the FL135 do not share the same base engine.* They are very similar, but the base engine for the 120 was the Dorset and the base engine for the 135 was the Dover.* The Dover incorporates some significant improvements over the old Dorset.

The FL135 is in all sorts of boats.* Probably as many if not more than have FL120s.* There are several 1980s vintage GBs for sale in our marina right now that have FL135s.* FL135s were used in Krogens and many other makes.* Keith of this forum has an FL135 in his Krogen 42.* And don't forget the rest of the world.* Look at international boat ads and many of them will list the engine as a "Dover" engine.* A lot of companies around the world marinized both the Dorset and Dover engines.* Lehman was just one of them.

The Dorset (FL120) engine wasn't a lemon in the overall sense.* It was a piece of crap as a truck engine, but it proved to be extremely well suited for industrial and agricultural use.* For many years, Ford of England supplied all the diesel engines to Ford, including Ford in the US.* This is why you can still find agricultural diesel shops in the US that carry parts for the Ford Dorset engine (it didn't go by that name in the US).* Ford used the engine in their own farm tractors and they were supplied to a number of combine manufacturers.* For example, some folks on the GB owners forum recommend a totally non-marine outfit in the Midwest somewhere as the best place to get new injectors or have injectors rebuilt for the FL120.* This shop specializes in repairing agricultural equipment.* Much cheaper, apparently, than using a marine service to do the same work.

4.* Lehmans don't overheat unless they develop a problem or they are operated in a manner than helps create a problem.* So you're right, the cause of an overheat is often operator error, if you will.* Of course there can be non-engine problems that can cause an overheat, too, if the operator doesn't take immediate action.* This is what's happened to us a couple of times.* In both cases the engine temp began to climb because of a restriction in the raw water intake.* We saw what was happening right away and shut the engine down long before the engine was endangered.* The temperature climb in these cases had nothing to do with the type of engine--- it would have happened with any kind of engine.

The problem with the FL120 (I can't speak for the FL135 is that if the engine does overheat, its design and construction is such that severe damage can occur fairly quickly.* It will not tolerate an overheat condition very long at all.* From what I've been told, the head gasket will go very quickly if the engine is overheated, and the head is very susceptible to warping if the engine overheats.

*
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Old 01-09-2011, 06:18 AM   #28
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RE: Horsepower versus Displacement

If it was known (how could it not be) that they were weak then why did'nt Lehman get another engine to marineize?

Lehamns work great at trawler 2 -3-4 gph , no problem.

But if you think its a 135 HP engine that will produce 135 HP all day long , your going to have big problems.
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Old 09-09-2013, 04:41 PM   #29
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80 ton Wooden full displacement Malahide ( 176, 000 # ) does 7.5 kn at 1400 rpm , 260 hp Volvo TMD 100

Will do that all day, reasonable seas . Haven't got a real handle on the mpg figures .
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Old 09-09-2013, 06:08 PM   #30
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Orcades,
Sounds like you're powered just right. From what I've read, heard and otherwise ingested I usually say 3 to 5hp per ton. Five is probably more appropriate for smaller boats like my 30' Willard and three is more likely on the mark for larger boats. But there are some variables that trump displacement like usage, B to L ratio, wetted surface, PC and many others depending on the general design of the boat.

Three to five hp per ton applies only to FD craft. Boats like many of the DeFevers that aren't FD but fairly close can just plug in a little more power like 3.5 to 6.5 hp. It would not be as easy to guess how much more a CHB or GB would need. More to be sure but how much would take a better guesser than me or perhaps a NA that actually knows this stuff but even then it would be a range of power. Not a specific amount. However the range of power would not be very wide. As you get further from FD it can get rather wide. But once you reach planing one needs at least enough power to get up on plane at full load.

One of the best ways to make some conclusions for most of us is to compare lots of boats over time and observe their performance relative to their power and hull shape.
If you have two boats w the same WLL and the same displacement but one is short on performance there is some other reason for the difference. Sometimes obvious and sometimes not. A Camano 41 is quite an efficient boat for it's general type. My opinion on why that is so is that they are a light boat. Directly relateable to "HP per ton".

But my re to the OP .. 3 to 5 hp per ton.
My opinion.
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Old 09-09-2013, 06:18 PM   #31
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The original thread was the ratio between the size of a boat and a small engine such as a Lehman 120.

Bay Pelican, a Krogen 42, has a Lehman 135 and I understand that it takes only 40 hp to drive the Krogen 42 at hull speed. The 135 was used after the 120 ceased to be manufactured.

With my Yanmar 27 hp wing engine I am able to cruise at 4.5 kts without pushing the rpms of the Yanmar.
Thus I would believe that a 50 some ft full displacement boat could be driven at hull speed by a Lehman 120. Don't know how much extra power would be available for hydraulics etc.

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Old 09-09-2013, 06:45 PM   #32
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I have her on the slip at the moment , had the hull surveyed and the steering and running gear checked out , doing some remedial work , I don't really know the displacement , so I am going to laser scan the hull , which will give me a true 3D image of the hull , and through the software it will give me a cubic met rage of the full irregular shape from the keel up to to a line which I will determine as the mean water line, which in turn should say approx 80 meters cubed @ 1 tom per cubic meter . There is about 30 ton ( I've been told of pig iron and old railway lines ) have seen it , lots all nested and fixed down .
Stability checks ???? Don't think I can get to that, true C of G kind of difficult to determine . I understand in the days she was built , she was launched as built , then the old experienced guy lined her up with his eye and told them where to position the iron bits in the bottom of the hull , and then said ... That's her , that's her line in the water .. !!
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Old 09-09-2013, 06:45 PM   #33
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I wouldn't feel comfortable without at least five horsepower per ton.
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Old 09-09-2013, 09:25 PM   #34
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So how many HP per ton do you have Mark?

And why do you think you'd not be happy w say 4?

Four would be 32hp for me and I,m sure that would be fine. The original Willard had 33 useable hp per ton and I've never heard of anybody complaining about not having enough power. And not for lack of ability either as Willard owners have complained long and loud about other things. Three hp per ton would be 24hp and at times that probably wouldn't be quite enough.
But if I didn't have an engine and somebody gave me a 24hp engine I'd use it and probably do 98% of everything I have done w Willy since we've owned her.


You're sounding like someone that should have a SD hull.

I have 5 and I'm sure I'd be happy w 4. 3.5 ????

I think if I had enough power to cruise 1/2 a knot under hull speed I'd be happy.

There was an old wood trawler in PMM some years ago that had an 8 cyl Gardner and was at a 2hp per ton and seemed to do nicely.
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Old 09-09-2013, 10:43 PM   #35
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So how many HP per ton do you have Mark?

And why do you think you'd not be happy w say 4?
Have 80 horsepower to push the 14-ton Coot. Hull speed is achieved with about 90 percent of maximum RPM. It's a good balance, with 50% less fuel consumption at one knot under maximum (hull) speed. Four horsepower per ton seems marginal to me as I wouldn't want to push the engine to extreme achieving hull speed.

Don't most of you all have several times more horsepower per ton to achieve greater-than-hull speeds?
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Old 09-10-2013, 05:57 AM   #36
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<Don't most of you all have several times more horsepower per ton to achieve greater-than-hull speeds?>

Only in ADVERTISED gross Hp, seldom at a realistic 24/7 rate .

Most folks dont care to double their fuel burn for an extra K.

Few marinized diesels , for lower power boats will have a set of power ratings that include anything but their auto or light truck rating.

One can stay out of trouble by expecting a non turbo engine to produces 1 hp for every 3 cubic inches of engine displacement at cruise .

The advertised rating may be much higher ,
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Old 09-10-2013, 07:48 AM   #37
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My 36 horsepower Volvo MD17 seems to be fairly well matched for a 7 1/2 ton boat.

Here's my speed in calm seas.

875 rpm 3.0 knots
1000 rpm 3.6 knots
1250 4.5
1500 5.2
1750 5.7
2000 6.2
2250 6.7
2500 7.1
2750 rpm 7.3 knots (hull speed?)

WOT (and max rpm rating) is 3000 rpm but I try not to push the 30 year old engine too much.

I wouldn't want extra horsepower; It would mean an even tighter ER.
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Old 09-10-2013, 08:50 AM   #38
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Quote:
...a Krogen 42, has a Lehman 135 and I understand that it takes only 40 hp to drive the Krogen 42 at hull speed. ...
I checked on BoatDiesel for the Krogen 42 with a loaded weight of 44,000 lbs and a water line length of 39'2".

The hull spend is ~8.4 knots and requires 87.3 shp. To cruise at 7.0 knots, the power required at the prop is 50.8. This assumes a clean bottom and smooth seas. The numbers are from BoatDiesel, Power Calculator.

So using 4 hp per ton is pretty accurate to calculate the needed hp for hull speed on a displacement vessel from what I can tell.
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Old 09-10-2013, 10:49 AM   #39
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It seems so Larry. If a single number is used 4 would seem perfect.

Re the narrow range of good power balance for FD boats there are variables that make unusual differences.

The Willard 30 is a 36hp boat but our own 38' TAD Roberts designed Yellow Cedar slips along on a little less power than the 30' Willards. A 28hp engine is specified for Yellow Cedar. An excellent design and LENGTH makes this boat stand out. Same displacement as the Willard but a lot bigger boat on about the same amount of power.

Usually though w more typical boats like the Krogen and the Willard 4hp per ton works very well and not much variation among other typical FD boats will be found. Indeed the Yellow Cedar and W30 are 4 and 5 hp per ton. So it's a good yardstick.

Semi Disp boats power requirements are harder to predict as the shape of the hull makes them close to or far from FD types. And marketing trends like the almost universal use of the Ford-Lehman engine. Practically the only power choice for trawlers was 120 or 240hp. Underpowered boats probably don't sell so most all trawlers were overpowered. But if one made a study of "typical trawlers" and their power a rule of thumb could be established but since the're almost all overpowered it would not be very meaningful.

But as I've mentioned before comparing lots of boats over time one can bring one fairly close to reality re power requirements if one knew how overpowered the compare boats are/were and how they compared to ones own boat as far as hull resistance differed.
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Old 11-14-2013, 08:30 PM   #40
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Quote:
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Roughly it takes 2 hp per ton (2240lbs of displacement) to move at cruise,

3 Hp per ton is about all most folks will be willing to pay for that purchase trawlers.

5 Hp per ton is about all a displacement boat can handle without making huge waves.
I'm a little overpowered for a full displacement vessel. My boat is around 3.5 tons on paper... maybe 4+ tons plus fully loaded. Original power plant was a 18HP Sabb diesel. I now have a MD2030 29HP Volvo, which equates to roughly 7 HP per ton. Extra HP has been useful handling some nasty weather and rough water. I spin a 16" prop on a 1.25" shaft that is likely too much torque for the smaller 20HP Volvo MD2020. I'm guessing the old Sabb could handle the torque quite well.

Maybe my boat's PO installed a larger engine to handle the relatively large prop/shaft?
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