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Old 11-20-2015, 04:44 AM   #21
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Lower power settings making 5 knots save much fuel in my experience although
Although it seems hard to just go 5 knots when it will get dark or have to be somewhere.
Fuel cost per gallon at the pump makes a difference to the overall fuel expense. We have seen some big changes lately.
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Old 11-20-2015, 07:06 AM   #22
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Except for the weight in the keel,and the riffing, a std (not a "racer" ) cruising sailboat hull would be the form for a high efficiency power boat.

Thousands of years of trial and error have gone into making that shape the easiest to push at Modest speed with Minor HP.

The further away the hull and power train is , the less efficient the entire package will be.

We do not ALL have motor sailors , as efficiency is not a big deal at under 2 or 3 GPH , and most Marine Motorists want to be UP on top of the hull, not down inside the vessel.

And until the MS is over 50-60 ft , the deck house is not large enough for most folks.
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Old 11-20-2015, 08:03 AM   #23
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David's answer (post 3) speak to the details... and then everyone's comments about relative fuel costs (compared to other stuff) speaks to the context.


Another context thought, this with twin 450-hp engines:
- cruise at 2400 RPMs = approx. 35 GPH @ approx. 22 kts = approx. .63 NMPG
- cruise at 2200 RPMs = approx. 27 GPH @ approx. 19 kts = approx. .71 NMPG
- cruise at 1200 RPMs = approx. 5.8 GPH @ approx. 8.5 kts = approx. 1.48 GPH
- cruise at 1000 RPMs = approx. 7 GPH @ approx. 7.5 kts = approx. 1.96 NMPG


Our theoretical maximum "displacement" speed (but it's a planning hull) is about 8.9 kts (waterline length 43.875').


I do not get "the same fuel economy" as would a single-diesel trawler of approx. the same length and with an engine size to provide appropriate horsepower.


OTOH, we don't do badly at putter-along speeds.


And while fuel isn't our largest expense anyway, the difference between a boat that burns 3 GPH at 8.5 kts versus our 6 GPH... is just a minor detail. To us. The rest of the boat, the whole package, is what guided our selection.


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Old 11-20-2015, 02:51 PM   #24
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I thought I learned here that the difference between a trawler and other boats was the nets!
Sorry, this trawler's not for sale.

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Old 11-21-2015, 11:12 AM   #25
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After a quick perusal of the other comments, there is another aspect of slow speed trawlerin'

Almost anything that floats can be run 'more economically' at low speeds. (Low RPM. low speed)

Why trawlers are generally slow speed is they run the 'smaller' engines at 60% to 80% rpm which is where diesels 'like' to operate as far as efficiency and longevity are concerned.

Running diesels at idle (or really anything less than about 40% rpm) makes the engines load up with soot, turbos get clogged, after and inter coolers don't work as well and cylinder temps are lower than design specs allow for. You actually see the evidence when watching a boat come out of a really long 'slow speed ' transit when there is a sudden increase in throttle (to full speed). Lots of black smoke, and a rapid spike in temps until the engine 'cleans up' and burns off the carbon from valves, turbos and exhaust.

So the question is: What type of boating are you anticipating? Fast boating, interspersed with a few quick jaunts? Or fast boating with some slow 'genteel' yachting thrown in?

If you want to just smell the roses as you boat, then a slow trawler is for you. But if you want to giddy up and go most of the time. (Then putt putt around some) get a planing hull.

Another BIG thing is how fast do you (and your SO) want to go? If you get a slower boat will you both be happy?
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Old 11-21-2015, 11:43 AM   #26
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Cappy:


You are so right. When we first got our downeast style Mainship Pilot 34 we went fast about 50% of the time burning about 12 gph. A few years later we now always go slow at or below displacement speed and burn 3 gph. But even now it is nice to have 370 hp available to go fast when we want to.


Having a big engine and a semi-displacement hull means that we burn almost twice what an equivalent full displacement small engine trawler would burn. But since the difference is only a few hundred dollars in a season of boating, it is almost insignificant compared with other costs of owning a boat.


So the point is to get the boat that will serve your needs whether fast or slow and don't worry much about the size of the engine.


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Old 11-21-2015, 01:19 PM   #27
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But since the difference is only a few hundred dollars in a season of boating, it is almost insignificant compared with other costs of owning a boat. David
But Dave.....that extra few hundred is my beer budget!
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Old 11-21-2015, 01:46 PM   #28
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Genecop,
If you're interested in or concerned about fuel consumption think light and small and slow mostly while searching for your boat. Also consider that the most distinctive feature than makes a trawler a trawler is it's weight.
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Old 11-21-2015, 02:05 PM   #29
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Genecop,
If you're interested in or concerned about fuel consumption think light and small and slow mostly while searching for your boat. Also consider that the most distinctive feature than makes a trawler a trawler is it's weight.
I also need to consider livability, so the size is a careful balancing act. Can you elaborate on "Makes a trawler a trawler Is its weight" thanks
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Old 11-21-2015, 04:50 PM   #30
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Is the fuel economy of a trawler based primarily on its lack of speed? If you took say a Hatteras and only cruised around 8 knots would you get the same fuel economy? I do understand that a Trawler will generally have greater range due to size of fuel tank. Thanks
You might find this discussion on the newer ultra-efficient designs of interest:

New Long Thin, Hyper-Efficient Trawler

Here are the fuel burn numbers:

"Starting at $850,000 (New Zealand $, or about $570,000 US) , its affordability is enhanced by the boat's extraordinary fuel economy.

In flat water, lightships, on this 58ft, 14-tonne vessel, we recorded:

• 7.2kts using 0.55 litres diesel per nautical mile

• 8.1kts using 0.67 litres diesel per nautical mile

• 9kts using 0.84 litres diesel per nautical mile.

Read More:

The Naked Cruiser
Cruise the world on half a litre of diesel per nautical mile


http://www.stuff.co.nz/sport/boating...-naked-cruiser
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Old 11-21-2015, 06:25 PM   #31
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Here are the fuel burn numbers:

"Starting at $850,000 (New Zealand $, or about $570,000 US) , its affordability is enhanced by the boat's extraordinary fuel economy.

In flat water, lightships, on this 58ft, 14-tonne vessel, we recorded:

• 7.2kts using 0.55 litres diesel per nautical mile

• 8.1kts using 0.67 litres diesel per nautical mile

• 9kts using 0.84 litres diesel per nautical mile.
Well, just like putting solar panels in your yard to "feed the grid" there's a payback time..... $370,000 buys a lot of gas, but I should be breaking even on my 127th birthday.... yipppeeee. If only I was 18 and wealthy.

Awesome technology though.
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Old 11-21-2015, 06:53 PM   #32
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Also consider that the most distinctive feature than makes a trawler a trawler is it's weight.
The fact that the recreational boating industry has, for marketing reasons, adopted the term "trawler" to describe a remarkably broad spectrum of powerboats means there is actually no correct definition of the word. Eric thinks it's defined by weight. The folks at Nordic Tug or Ranger Tug would disagree, as they consider their lighter, faster boats to be "trawlers," too.

There is only one definition of the word "trawler" that draws no arguments from anyone and that is that it's a type of fishing boat. Every other definition draws opposition from someone if not many someones.

Leaving aside the fishing bit, I don't use the term "trawler" in connection with recreational powerboats but if I did weight would not be part of the criteria in my mind for being this type of boat. I can see why Eric does and I don't fault him for it, but because the term has become so corrupted by using it to describe so many different types of vessels, I tend to think of the term as more the function of the boat rather than any one physical attribute.

In my opinion, the term "trawler" has become synonymous with the term "RV." RV encompasses a whole host of types and configurations. Trailers, fifth-wheels, single axle, tandem axle, tripple axle, pop-up trailers, and all the different classes of motorhomes. Out of all this, what is the one common denominator?

How it's used.

I think the situation is identical with boats and the term "trawler." It no longer defines a specific configuation or set of performance factors or physical characteristics. The marketing departments and ad agencies have seen to that.

What is the one common denominator that encompasses our 43 year old. twin-engine Grand Banks and the brand new Ranger Tug down the dock and a Nordhavn and a Bayliner 3888 and an American Tug and a Nordic Tug and a CHB and a Californian and Eric's single engine Willard and Mark's steel-hull, sail-assisted Coot, all of which are referred to as "trawlers" today?

Same as the RV. How it's used.

That's the only all-encompassing definition left now. Every other definition is open to argument. Eric says weight. A number of manufacturers whould disagree. Some say low speed. A number of manufacturers and owners would disagree. Some say physical appearance. Manufacturers and people with boats that don't look that way would disagree. Some say low fuel consumption. The owners of Grand Banks boats with big engines who like to cruise at 16-18 knots would disagree. Some say displacement hulls. People with semi-planing and planing hull boats would disagree.

Some might say range, and this is actually plausible as it ties in with how "trawlers" are used. So are terms like "comfortable," "good visibility," "good ride," and so on. But none of these terms describe a particular kind of boat, they describe the attributes one wants in a boat and there are lots of ways to get them.

The term I prefer for the type of boats most participants in this forum have is "cruiser," or as Eric llkes to say, "heavy cruiser." But these terms,too, are not definitions of physical or performance attributes but how a boat is used. You can cruse at 6 knots and 1.5 gph and you can cruise at 40 knots at 60 gph.

So when one sees the term "trawler" used in a manufacturer's sales brochures or ads, or applied to an ad on Yachtworld, or even as used by the members of this forum, just think "RV." You will be 100 percent correct every single time.
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Old 11-21-2015, 08:04 PM   #33
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Marin,
Good post.
The boats we call trawlers now were called "heavy cruisers" as in your post above. They separated normal cruisers from what we call trawlers by referring to their greater weight in the name that was used at the time. Should have never changed IMO. The old wood "Monk boats" of about 40' were typical of the heavy cruisers.
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Old 11-21-2015, 08:28 PM   #34
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Even if it doesnt walk like a duck or quack like a duck you can still call it a duck if you want it to be a duck bad enough. The folks that actually own "DUCKS" know what a duck really is.
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Old 11-21-2015, 08:56 PM   #35
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I just figured out that I did 133 hours this year. That was including about 3 hours a day of genset (I got a nice big battery charger that chopped 2 hours off the charging time) and my Hurricane heater in the evening in the winter, probably 4 hours/ day on average. That means that the fuel cost was about $20.50 per hour or about 20% of the average yearly costs I have on a recurring basis. Including haul outs and zincs. We currently have fairly low fuel prices but if it went up 25% to where it was before the crash, it would only be $25 per hour, which is pretty darn cheap and getting to the point where serious attempts to cut fuel consumption will result in being cold (less heater use) or killing the batteries (less genset). Each device is rated at 1 gallon per hour and I think that's very close. So, before I even start the engine I have committed to 7 x 4.6 litres or 32 litres for $35.

Go back and see post number 5, he's correct.
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Old 11-21-2015, 09:47 PM   #36
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I've had this exact same question regarding fuel consumption recently comparing displacement, semi displacement and planning hulls. From the research I've done so far my conclusion is it will depend on a lot of factors and really comes down to the individual boats you are talking about. The only way to determine fuel economy on that individual boat is to find someone who has one and operates it or operate it yourself for a time. You will find there are planning hulls that can be operated even more economically than some full displacement hulls around the same size but it all comes down to the hull/engine combination and how it is driven. This is a couple of links to a site with people who have had and operated both planning and full displacement boats and know exactly their operating figures.

Bayliner 4087 | MV Dirona
MV Dirona Specifications and Features

The other thing I have found is that the idea that operating high powered engines at low power for long periods does them damage is something of a myth. I wouldn't say it completely unfounded but I have done it myself with Volvo and Caterpillar engines for many thousands of engine hours with no ill effects. I have also talked to and found many others with different engines but the same experience.

My suggestion would be find a boat you like and research that one to find its true economy the way you want to operate it.
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Old 11-21-2015, 09:50 PM   #37
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So a Grand Banks is not a trawler?
No on many counts. Nor as they normally advertised as one.
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Old 11-21-2015, 10:04 PM   #38
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Take the same path in a single engine trawler like the N46 at lets say for discussion sake 3.0 NMPG and the monthly fuel cost drops to $465 a huge difference! .

Kevin it would seem to me that people do not buy Nordhavns to save money. The general consensus among N owners is they buy their vessels so they can go long distances without the need to refuel. This long distance travel requires about a 1.5 to 2 nmpg fuel burn at 6.5 to 7 knots.

Purchase and upkeep of a Nordhavn are not small sums so from the standpoint of frugal boating, it is not done in a Nordhavn. Unless of course it stays at the dock which defeats the purpose of owning one.
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Old 11-21-2015, 10:23 PM   #39
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No on many counts. Nor as they normally advertised as one.

Tom I'm think'in the classic GB's of the early 70's is about as trawler as you can get. Wer'nt they the original trawler? Sure there were Willards that pre-date the classic GB's by 10 years but by classic I'm think'in a typical trawler like a GB, CHB and Marine Trader.

Advertiseing dosn't count as it's bottom line is manipulation not a tool for truth and fact.
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Old 11-21-2015, 10:34 PM   #40
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Tom I'm think'in the classic GB's of the early 70's is about as trawler as you can get. Wer'nt they the original trawler? Sure there were Willards that pre-date the classic GB's by 10 years but by classic I'm think'in a typical trawler like a GB, CHB and Marine Trader.

Advertiseing dosn't count as it's bottom line is manipulation not a tool for truth and fact.
You are right Eric, the early ones were indeed trawleresque if you will. But then came the 80s and any thought of a GB trawler quickly became a fleeting memory.
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