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Old 06-15-2014, 12:31 PM   #41
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I don't understand why the smaller engines will use 2 gph less??
Are you replacing gassers with diesel?
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Old 06-15-2014, 12:38 PM   #42
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If you want to convey information about the nature of a boat it is best to define hull type and a few other parameters such as displacement LOA LWL beam and draft. The above deck configuration along with basic drive system. Trying to define to someone the nature of a boat called a trawler without telling them it has IPS drives and a planning hull is mean less out side of sales mumbo jumbo..
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Old 06-15-2014, 12:50 PM   #43
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I don't understand why the smaller engines will use 2 gph less??
Are you replacing gassers with diesel?
No real reason - I was just playing with likely numbers and hoped the replacement engines used would be that much more efficient.
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Old 06-15-2014, 01:16 PM   #44
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going from 2 stroke to 4 stroke diesels does make a difference but still probably not worth the cost.

Across all 4 stroke diesels you probably wont find a big difference in HP produced per pound of fuel. Look up BSFC ( brake specific fuel consumption). Turbo charged is a bit more efficient at turbo loads but still not a huge difference.
from brand to brand and model to model there is a large difference in max rated power but little difference in efficiency. Full electronic control may be a bit more efficient than old mechanical engines but I haven't looked at their BSFC.
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Old 06-15-2014, 01:30 PM   #45
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All in all - Repowering a used boat seldom comes out in a positive financial sense regarding profit or even break even in the long run. Sooo... take care of your engines and enjoy boating
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Old 06-15-2014, 01:45 PM   #46
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I would really like to go from a best of 1 mpg to maybe 2 mpg, that would be great. Right now I'm considering using 3-71s. I can use the Allison MH gears, which I like for several reasons, one being the "get home" feature. I will probably need 3 or 3.5 reductions. The gears now are 2 to 1 ratio. 3-71s rated at around 90 to 100 hp each should be about right. I'm planning to use 7E55 injectors, which are the latest mech. injectors for the DDs. They were designed for metro buses in Cali. No smoke. Make 30 to 40 hp per cylinder non turbo. At that rating a 71 series will run a very long time. Will probably set max rpm at 2100 high idle. Prop it for 1800 at 9 knots or so. Best economy should be at 8 knots. Cost is not a big deal, I'll do it all myself. Its fairly easy on this boat. I can buy the 3-71s plus the marine parts used, cheaply. Availabilty is not a problem. You just need to know what parts are needed. The economy increase comes from only having 6 cylinders instead of 16. Parasitic drag comes into play. And, twin turbo 8v92s are just not meant for economy.
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Old 06-15-2014, 02:32 PM   #47
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Sounds like you really know your stuff. Those 8v92 are probably way out of their efficiency range at 8 knots, not that they were ever very efficient. The little 3s will be much nearer the mid range. Be even better if you could go to 4 strokes but staying in the Detroit family will surely be easier.
I guess that you will also loose over a 1000 pounds that will help too.
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Old 06-15-2014, 05:23 PM   #48
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And the boat will be lighter. Always a plus re efficiency.

Smaller engines are more efficient.
If you load them at the their most efficient rpm.
Bigger engines make a better heat sink and being a heat engine the more surface area exposed to combustion temperatures the more heat is lost. And heat is power. But also lower combustion temperatures will be present in a bigger engine not working hard. So it's a balance of combustion temp and heat loss. Usually smaller engines will burn less fuel. Take a 36GB w twin 55hp JH Yanmars pushing the boat 7 knots. There will almost certainly be less vibration, noise and fuel consumption. And the boat will weigh 2000lbs less.
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Old 06-15-2014, 07:39 PM   #49
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Trying to define to someone the nature of a boat called a trawler without telling them it has IPS drives and a planning hull is mean less out side of sales mumbo jumbo..
Describes the current versions of the quintessential trawler....Grand Banks.
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Old 06-15-2014, 07:50 PM   #50
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Grand Banks never made a trawler. Lehmans Cats Cummins, whatever, not a trawler. It is a planing hull, pure and simple.
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Old 06-15-2014, 08:04 PM   #51
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Grand Banks never made a trawler. Lehmans Cats Cummins, whatever, not a trawler. It is a planing hull, pure and simple.
Love it !
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Old 06-15-2014, 08:10 PM   #52
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The reality is no one here gets to say one way or the other...they may have their OWN idea...but the boating world has already made up their mind..

If you go out in the real world and say Grand Banks aren't trawlers...you'll be laughed out of just about every place I know or have been.

Grand Banks owners will occasionally tell you they are not trawlers...we have (or had) a member that was adamant that GB and their "club" never claimed to be or used the word trawler in their (I don't know and don't care one way or the other) literature.

99.9 percent of my boating friends and associates don't care either.
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Old 06-15-2014, 08:12 PM   #53
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Grand Banks never made a trawler. Lehmans Cats Cummins, whatever, not a trawler. It is a planing hull, pure and simple.
I`m off for a chat with the IG with Lehmans: "Plane you bastard, plane".
NS, "gentleman`s cruiser" might be another term ( cuts me out though).
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Old 06-15-2014, 08:39 PM   #54
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Grand Banks never made a trawler. Lehmans Cats Cummins, whatever, not a trawler. It is a planing hull, pure and simple.
My post was intended to suggest the irony of it all. As psneeld points out, the vast majority of the boating public seems to think it is a trawler...planning hull, IPS, and all. After all it sports the penis extender topsides and interior.
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Old 06-15-2014, 09:10 PM   #55
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I went into the Bible, with Concordance at hand, and could not locate chapter or verse defining "Trawler". Therefore It Simply Ainít!!

But rather... it must be a figment of our imaginations.

Now, there you have it!!
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Old 06-15-2014, 09:19 PM   #56
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Wifey B: You dudes are getting way too hung up over a silly word that has no agreed definition. It doesn't matter. Darn. Trawler, displacement, semi displacement, planing, semi planing, fast trawler, twin engines, single, delta anchor, danforth. Just talk specifically what you want or don't worry about it. This is like arguing over how many stars there are in the universe. We're not on a "trawler" right now, but it will do anything a trawler will. Now I would agree Baden is not a trawler. It's a ..... well, I can't use those words here, but definitely not a trawler. I would agree trawlers should float upright.
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Old 06-15-2014, 09:28 PM   #57
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NOT a trawler:

correct.. not a trawler... but capable of massive " smiles per gallon"

HOLLYWOOD
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Old 06-15-2014, 09:31 PM   #58
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Well, Kadey Krogen never put a pair of 375 hp 3208s in a kk42. It would not have made any since. GB on the other hand could benefit from more power, if thats what you wanted. Because it is a planing hull. And, you could get 300 hp from the venerable Lehman with a little tweakin, and a turbo. The rest of the drive train would be hard pressed to stay together and longevity would be seriously diminished, "bout like a 3208 Cat at 425 hp. At the average of 100 hours per year it would still outlive the warranty. Dont get me wrong, I do love the GBs and would like to own one someday. I will not call it a trawler. I do like the debate tho !!!
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Old 06-15-2014, 09:36 PM   #59
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What would you call a Gulfstar 36 MarkII? I'm curious because it seems like a trawler to me...
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Old 06-15-2014, 09:47 PM   #60
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What would you call a Gulfstar 36 MarkII? I'm curious because it seems like a trawler to me...
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Bill - Personally believing there is no true definition of a "Trawler"... that it is a pliable, whimsical term... I'd call it a "Pleasure Cruiser"... Same as I call mine! - Art
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