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Old 02-13-2017, 06:54 PM   #1
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Grand Banks Fuel Consumption

I am looking to move into a GB 42. Seriously before summer hits. I have settled on a fiberglass 42 and can't seem to find a single diesel in my price range. I am looking in the (1974 - 1986) range.

What are the fuel consumption trade offs for the models I have found in my price range?

twin Lehman 120 Model 2715?
twin Leyland 6T-165 FWC?
twin Detroit V8 Natural aspirated 6.7?
twin Cat 3208 N?

Thanks
Kurt
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Old 02-13-2017, 06:58 PM   #2
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They will all be the same, virtually, for any given displacement speed. Get the Lehman if there are two, otherwise you won't be able to move around down there.
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Old 02-13-2017, 07:02 PM   #3
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I have a 1981 GB with twin detroit 453's. I average 3.5 gph when on the move and that is with 15k generator running ,most of the time. Twins really improve handling in docking or tight quarters when no bow or stern thrusters are available. I've owned it for 7 years and still in love with it. That's at 1500 to 1650 rpms. Hope that helps.
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Old 02-13-2017, 07:08 PM   #4
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I have a 1981 GB with twin detroit 453's. I average 3.5 gph when on the move and that is with 15k generator running ,most of the time. Twins really improve handling in docking or tight quarters when no bow or stern thrusters are available. I've owned it for 7 years and still in love with it. That's at 1500 to 1650 rpms. Hope that helps.

Thanks, definitely helps. I read somewhere else 8-9 gph fuel burn. Ouch!
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Old 02-13-2017, 07:12 PM   #5
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Doesn't matter a whole lot. It depends mostly on the speed you want to make. Nevertheless, running powerful engines very slow to be economical seems a waste to me.
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Old 02-13-2017, 07:30 PM   #6
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The speed you operate the hull at is what will determine fuel use. Decide you have to run at 10knots and fuel use will jump hard. Keep boat speed to a bit under 8k and fuel use should be reasonable,. 2.5 to 3.5 gph.
Leave the V8 Cats and DD alone. Good engine but big and will leave lousy access. Access is important
When work must be done whether by you or paid for by you.
Lehman's have proven themselves over many years in this and similar boats

Working from darn tablet but will add that DD is , I remember, is an unsupported engine now. The Cats at least are still supported. Leave them alone.
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Old 02-13-2017, 08:10 PM   #7
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In my experience DDs have parts readily available and mechanics who know them as well. Not sure I can agree with the "leave them alone advice although other choices such as the Lehmans is certainly a good one too
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Old 02-13-2017, 08:23 PM   #8
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The speed you operate the hull at is what will determine fuel use. Decide you have to run at 10knots and fuel use will jump hard. Keep boat speed to a bit under 8k and fuel use should be reasonable,. 2.5 to 3.5 gph.
Leave the V8 Cats and DD alone. Good engine but big and will leave lousy access. Access is important
When work must be done whether by you or paid for by you.
Lehman's have proven themselves over many years in this and similar boats

Working from darn tablet but will add that DD is , I remember, is an unsupported engine now. The Cats at least are still supported. Leave them alone.
Good advise from Clark. Ford Lehman engines seem to run forever......Lots of Lehman owners at this site. Parts availability is huge for older engines, and I think they are still readily available for Ford Lehmans. I had Detroit 8v71s in the past, and chartered boats with v8 3208 Cats........big, heavy conservative engines, but they take up a lot of engine room space that you'd rather have for elbow room and storage. A friend of mine owned the biggest trawler charter operation in Annacortes in the 1980's and his comment was that he wished all his boats were Lehman powered. That sums it up.
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Old 02-13-2017, 08:31 PM   #9
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I've had both DD's and Lehman 120.
My current twin 2715E Ford Lehmans 120Hp burn .8 GPM at 1800rpm doing 7kts +/- depending on wind etc. They are pushing a 50ft 50000lb Cheoy Lee.
Always found it a battle with oil leaks on the DD's and heavy fuel consumption per mile.
Bigger lumps in the boat, and hard to get round to maintain, was a larger different boat.
However my lehmans have all good round access and are easy to maintain. Everytjhings simple and parts readily available.
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Old 02-13-2017, 10:26 PM   #10
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The engines are ok. It,s the size which I pointed out. WIDE. Which can seriously crowd the E.R.

My memory may be off but that particular DD had support trouble. Not the others.
I could be wrong but I will stand by my comment about twin v8 engines in those hulls.
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Old 02-13-2017, 10:36 PM   #11
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That you can`t find any singles suggests most owners preferred twins, rightly so imo.
Engines are but one factor in choosing a boat, but I like my Lehmans, anyone can fix them, parts are available, and they are not turbo. And as consumption is a concern, they are as mean as. But even if you end up with something else, you will find fuel is one of the lesser expenses. Any with Cummins engines, they`d be worth having.
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Old 02-13-2017, 10:38 PM   #12
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Biggest problem in the GB 42 is that the cabin is so narrow that the only access to the engines is a small floor hatch at the front of both engines, running across the galley floor. once you get down into the ER you are trapped between the engines. Even sitting between two Lehmans is cramped. I can't imagine many of us being comfy between wider engines.
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Old 02-13-2017, 10:52 PM   #13
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That you can`t find any singles suggests most owners preferred twins, rightly so imo. ...
Yes, 30-year-old boats with twin engines and fly bridges are plentiful and relatively cheap now. Times were better decades ago for the upper-middle classes.

I "rightfully" selected a boat with keel-protected single propeller and rudder. Have avoided underbody damage unlike my twin-engine friends.
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Old 02-13-2017, 11:57 PM   #14
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Thanks, definitely helps. I read somewhere else 8-9 gph fuel burn. Ouch!
GB 42 Yes 9-10gal this figure is 42 GB consumption of 10 knots with a bigger engine alternatives.

I have test driven the consumption of 2 x ford "lehman" sabre 135hp and consumption 4.9 gal 8 knots, this boat have consumption gauges.

I have the impression that the GB42 has two different under water hull shapes. At some point, when you wanted to go to a bigger engine and a faster speed of hull shape modified SD more than in the past?
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Old 02-14-2017, 12:03 AM   #15
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There are some GB 42's with singles but it will be a very small percentage. Two I know of were in the PNW. One had a single Cat 3208, the other an old JD 6404. One in Australia had a Gardner 6LXB. At any given speed their fuel consumption would be about the same as twins. The ER was more spacious though.

But you do need some secondary form of propulsion, and I was never convinced the mast and possible sail on a GB42 would move it much at all. None of the single GB I was looking at had wing engines. Mark's Coot has a better sailplan.
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Old 02-14-2017, 02:03 AM   #16
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I have Cat 3208 naturals. Combined, I burn about five to six gallons per hour. That gives me about eight to ten knots.

I wish the total annual cost of owning this boat was as cheap as the fuel...!
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