26 Duffy outboard .

Powderpro

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No, I doubt that in a DE boat that the OB would be nearly as economical as a modern diesel. Probably 35%-40% more fuel used.
Although an OB would be fast, when the weather intensifies and you are 40 miles from shore, I would far prefer to be in an IB diesel powered boat. That is if the there was room to service the engine.

If the weather intensifies 40 miles offshore, I don’t really want to be in a 26’ no matter what it’s powered with. I want to be in a 35’+. Whatever the propulsion, I would be very careful going a long way offshore in a 26’.
 

WoundUpMarine

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26' Duffy, 23' Seaway, 14' Holland
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Powderpro

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When Atlantic boats launched the first 26/29 Duffy outboard with twin 150’s, Nate posted on this forum the boat hit 31 knots, and at 25 knots was burning 15 gph. I’m assuming that boat was pretty light, but most sea trial numbers are.
 

duxbait

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I think that boat looks fantastic. I am a big fan of the "clean" look it has. As far as outboards go, if you hang one off a bracket it shifts the COG farther back, makes the motor far more likely to being dunked by big seas or while coming off plane, and makes it harder to work around the back of the boat. Motors on a "notched" transom are far better. Hopefully the downeast world doesn't go bracket crazy like the deep V world has as outboards grow more and more common on small downeasts.
 

cb34

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13'6" from main bulkhead or from back of wheel house sides ? Nice little boat...
 

c1steve

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When Atlantic boats launched the first 26/29 Duffy outboard with twin 150’s, Nate posted on this forum the boat hit 31 knots, and at 25 knots was burning 15 gph. I’m assuming that boat was pretty light, but most sea trial numbers are.
AJ28 numbers are more like 9 gph at 24 knots. That is what the website states, and forum members say they get very similar numbers as advertised.
 

Powderpro

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This is a nice AJ28 launched a few years back with a Yanmar, owner claims 20 knots at 8.7 gph. He also said to get 3 mpg he had to slow down to about 12 knots. Boat looks pretty basic and light. My guess is the 29 Duffy at 20 knots with outboards would be burning 11-12 gph.

 

leaky

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The efficiency part - outboards are indeed efficient, but you gotta figure in that they cropped the keel. The same boat w/ the keel cropped as an IO Diesel (not that I advocate IO) likely would be more efficient than any other model.
 

leaky

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I think that boat looks fantastic. I am a big fan of the "clean" look it has. As far as outboards go, if you hang one off a bracket it shifts the COG farther back, makes the motor far more likely to being dunked by big seas or while coming off plane, and makes it harder to work around the back of the boat. Motors on a "notched" transom are far better. Hopefully the downeast world doesn't go bracket crazy like the deep V world has as outboards grow more and more common on small downeasts.

With outboards - if you have them on the transom with an engine well, they are just as much in the way as with a bracket, same problem - engines are set back away from where you stand.

If you have them on the transom without an engine well, now your transom height is dictated by the shaft length - the cutout anyway - that can be really problematic. Maybe w/ a DE you could put a 30 inch shaft outboard and still have good freeboard as they are really shallow back there. With a deep V that's just not possible. This Duffy looks good/seaworthy that way, some other boat wouldn't.

But the dunking part, nah, that's a theoretical problem and not an actual one. Sure maybe someone put 20 inch shafts on a bracket with a real deep V, so located their engines way down low, same problem happens without brackets...

That rare event where the water really sloshes up against the back of an outboard does nothing, they are made for it, and even if it enters the vents - it drains in a safe manner so they do not suck it up while running. Usually outboards on a bracket are set higher than they would be set if on the transom - they are actually further above the waterline. Really if anything a boat w/ engines on a bracket is safer than with a cutout on the transom, the transom is full height, the boat is going to react before a wave meets the transom.
 

c1steve

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For an OB setup, I believe a full flotation bracket that is continuous with the hull would be the most effective. Ideally the bracket would be part of the hull, but either way the waterline length of the boat would be 32" longer, so it would ride better, and on acceleration the hull would stay flatter.

On the AJ28, they mostly use high revving Yanmar engines. A larger displacement and slower turning motor would be more efficient, but it probably would not fit.
 

leaky

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For an OB setup, I believe a full flotation bracket that is continuous with the hull would be the most effective. Ideally the bracket would be part of the hull, but either way the waterline length of the boat would be 32" longer, so it would ride better, and on acceleration the hull would stay flatter.

On the AJ28, they mostly use high revving Yanmar engines. A larger displacement and slower turning motor would be more efficient, but it probably would not fit.

If you basically extend your hull you get the benefit of that.

On the flip side you forgo the ability to run the props in cleaner water that comes w/ a standard bracket that sets the engine(s) back away from the hull.

Both of those can be of significance. Potentially end result feels pretty similar though.

I'd be seeking a standard setback bracket if I was doing a retrofit, a much simpler fitment/design when your engine bracket is out of the water while running and you have the flexibility of mounting it higher or lower on the transom since it need not line up w/ the boat bottom - and there's a benefit there too, especially a fast V hull. Potentially if I was building a new outboard DE I might have the hull extended to make for an integral bracket.
 

c1steve

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On the flip side you forgo the ability to run the props in cleaner water that comes w/ a standard bracket that sets the engine(s) back away from the hull.

Both of those can be of significance. Potentially end result feels pretty similar though.
I have heard that argument many times, but I am very suspicious of it, at least in a DE boat. The props are well below the hull, I would think that the disturbed water only extends about 2" away from the hull. It would be most interesting to do a comparison test, two identical hulls, one with a separate bracket. and one with an extended hull mount.

Personally I believe people started by building aluminum brackets, and mounted them above the hull boat so the drain plug could be accessed. Everyone then followed with the same style and it became the norm.
 

PatriciaLynn

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I think it’s great the way it is. I think boats say 29ft and below should all be outboards myself. Way cheaper to build, easier to maintain, no engine box , no shaft, shaft seals, rudder, rudder box, crusty engine beds etc , almost no noise, shallower draft, they are faster, you can trailer it yourself, the list goes on. I don’t miss crawling thru my asshole to change the oil and $2000 props either .. just my opinion
Great sales pitch, really.
 

fordy

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Extending the hull makes a ton of drag, that's been my understanding of why brackets always clear the waters surface when on plane. Solves the drag problem but you still get bouyancy at rest
 

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Bill

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If you take 2 hulls, identical, but 1 is longer than the other, the longer one should go faster..
 

Diesel Jerry

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