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Passages
06-29-2008, 11:14 PM
Just wondering how much hp would be needed to push a 58 along at trawler speed. Was thinking a pair of 6-71n @ 310 might work but not sure.

Thoughts?

(Yes, even though I'm currently boatless, there is a specific reason I ask)

spartonboat1
06-29-2008, 11:18 PM
You are right on. Check the brochures on this site and I believe the 58 LRC's run 6-71N's, and for sure the 65LRC runs 6-71's. 2.8k gals fuel in the 65LRC, so $11-14k per fillup or more. Enjoy...

Genesis
06-29-2008, 11:22 PM
A pair of 310s are vastly more power than is required to move that boat at displacement speeds.

Passages
06-30-2008, 07:41 AM
A pair of 310s are vastly more power than is required to move that boat at displacement speeds.
4-53's then?
Buddy had a 40' Trawler equipped with 4-53's and it seems about right. Since a 58 would be about 3x the weight, thought I'd need to go the next size up.

We could consider Yanmars, or other. I'm just more familar with Detroit iron.

The link below is what got me thinking:
http://www.yachtworld.com/core/listing/boatFullDetails.jsp?boat_id=1933648&ybw=&units=Feet&currency=USD&access=Public&listing_id=2225&url=

Boatsb
06-30-2008, 07:50 AM
671N's at about 280 HP would probably do the job and last nearly forever. I would also look at luggers as the newer tech may get long life and better efficiency. Turbos would not be on my list for that type of work since weight would not be the issue and longevity and simplicity of maintenance would be my measure.

Genesis
06-30-2008, 08:06 AM
Well you want more power than "minimum required" obviously; naturals would be on my list for this, and I'd probably be looking at Lugger and a few other possibilities.... newer tech is definitely going to be more "social" if you're starting with a clean slate in the engine room.

Brian Degulis
06-30-2008, 11:26 AM
You need about 300HP total that will actually give you more than hull speed probably around 10 kts with room to spare. 671s would be a poor choice to much power and in efiecent old technology. One of the modern electronic engines like Cummins QSB 230 would be a great choice. You would have 460 continous HP available and you can run as slow as you like with no fear of being to lightly loaded. If these were available when Hat was building the LRCs they would have used then for sure. If my 1271 TIs ever need rebuilding I would replace them with the QSBs and soft mount them on Aqua Drives. Quiet smooth and very low fuel burn.

Brian

ThirdHatt
06-30-2008, 11:38 AM
You need about 300HP total that will actually give you more than hull speed probably around 10 kts with room to spare. 671s would be a poor choice to much power and in efiecent old technology. One of the modern electronic engines like Cummins QSB 230 would be a great choice. You would have 460 continous HP available and you can run as slow as you like with no fear of being to lightly loaded. If these were available when Hat was building the LRCs they would have used then for sure. If my 1271 TIs ever need rebuilding I would replace them with the QSBs and soft mount them on Aqua Drives. Quiet smooth and very low fuel burn.

Brian


Those Cummins would be a great choice, but they would cost more than the boat that he wants to put them in! A pair of 6-71's worked just fine for the LRC's and they'll work fine in that boat as well. I bet he can find a fresh pair of 6-71's and get them in the boat and still have only spent $100k for the whole thing!

REBrueckner
06-30-2008, 12:38 PM
At,say, a hundred hours annual running, it would take several lifetimes to recoup the cost of brand new super duper ultra modern hi efficiency diesels via fuel savings. At a thousand hours annually, they might begin to make a lot of sense.

Nothing wrong with 6-71 naturals especially if set up for reduced HP...smaller injectors,etc....say workboat/commercial rating rather than recreational...

Trawler speed is 6 or 7 maybe even eight knots; doesn't take much HP for that low end...but if you want to move,say ten, knots, you'll cut your travel time nearly in half but likely use double or more the fuel...what's most important is a personal choice.

Passages
06-30-2008, 01:22 PM
75 hours is the most I've ever put on the boat in a year, so maybe 100 is right if I'm going slower.

I bet the old girl had 12-71's which should be a relatively easy swap for 6-71's.

Unfortunately I tossed my latest copy of Boat's & Harbors but I seem to recall rebuilt 6-71's going for about $18k each. Can anyone confirm?

If I had to chose between a pair of 6-71's @ $40k, vs new high tech at 80, the DD's win.

Boatsb
06-30-2008, 01:26 PM
I think I saw a pair of 8V53's for about 20K rebuilt. 289 HP and run forever if you take care of them. I have one with over 7K hours and it passes the genesis cold start test.

Genesis
06-30-2008, 01:26 PM
I'd be inclined to go for reman'd mechanical Cummins, which are likely not much if any more than rebuild 6-71Ns.

The advantage of the 4s will be less weight and lower fuel burn, and if you can get those for close to (or actually) the same money, then its an easy decision.

ThirdHatt
06-30-2008, 01:55 PM
The 53's are just too old to spend that kind of $$$ on IMHO. Some would argue the same for the 71's but they are probably the most bang for the buck and would "fit" that boat in several ways.

The mechanical Cummins are great engines, but it would have to be a 6B 250 or 270hp to compare. None of the 4cyl would make the power. Those 6B's are turbocharged vs. the natural Detroits. I have a pair of 4B250's in a 31' Ocean Master and those little engines are high strung! It's basically the 6B 370hp with two fewer holes per side so they are at the limits of the design. The exact opposite of what one would want for a trawler and/or extreme longevity. The natural 6 and 4 cyl B-series are all under 210hp I believe and probably would not be adequate for that 58TC. Then again many 58LRC's did have 4-71's with BIG wheels and BIG reduction gears!

I say go give the guy $50k for the boat, find a nice low hour pair of 6-71's w/gears for $25-30k or so and drop'em in!

StratPlan61
06-30-2008, 02:22 PM
There is pair of used (220hrs SMOH) 8V71s on this website in the Parts For Sale area for $9,000. I think I'd buy the boat, have these 8V71s looked at very carefully by a competent Detroit Diesel expert and you know the rest . . . . . . . .

Passages
06-30-2008, 02:55 PM
Something else just occurred to me...

How are 58's in sloppy conditions at 9 knots? These appear to be a bit top heavy (Could be wrong) and perhaps were never intended for life in the slow lane. A MY is not the same as an LRC afterall.

Any 55-60 owners care to comment? Ang??? Freebird???

Pascal
06-30-2008, 03:10 PM
teh 8V71Ns found in early 53s like mine dont' make much sense. they're big and heavy and can't get the boat beyond 14 kts anyway... Once you go over 9kts, fuel flow goes up 2 or 3 times faster than speed so there is no point in even trying...

you may want to check the numbers but i think 8V71Ns produce just under 100 hp at 1500rpm, which yields about 9kts. I'd say that anything capable of making 150hp+ woudl work well in an old 53 or 58.

a little bigger is nice since you will have reserve power and won't push it hard at regular cruise but i dont' see why you'd want to put a 671 in there, still too big.

doc g
06-30-2008, 04:23 PM
I thought I read somewhere that Cummins 230 B's could be had for 25K each?? Anybody know what they actually cost??....................Pat

yachtsmanbill
06-30-2008, 05:25 PM
Something else just occurred to me...

How are 58's in sloppy conditions at 9 knots? These appear to be a bit top heavy (Could be wrong) and perhaps were never intended for life in the slow lane. A MY is not the same as an LRC afterall.

Any 55-60 owners care to comment? Ang??? Freebird???


I ran the 58 up to Chicago at 11mph-1400 rpm @ 16 gph and it was rock solid... even on the Mississippi at 20+ feet above flood. Only once it was a tad sloppy with a 60 foot clorox bottle rolling around us coming out of a lock.
I like the 58 tc with no engines. A pair of 6-110s would do just fine.
Naturals with 275 hp at 1800 and pretty cheap with a ton of parts still available. ws

Passages
06-30-2008, 05:36 PM
Thanks Bill,

Whats the hull speed of a 58?

krush
06-30-2008, 06:03 PM
You spending the time and effort (and money) to repower the thing, go with new or reman or engine. What about a John Deere or Duetz or even Izuzu if they make marine stuff? I wonder if Kubota makes marine engines.

I don't think Lugger actually makes their engines.


You could get a detroit series 40 (it's a 4cyl 60 used in metro busses). If you could get away with 4cylinders that would be nice, but inline 6 should be fine.

The goal is simplicity and fuel efficiency. Every modern diesel is going to have a turbo, so you can't get away from that.

You also could consider going dry-stack and keel cooled.

MikeP
06-30-2008, 06:05 PM
I like to tell this story...

When we bought our (non-stabilized) 53MY and took it to NY from about 30NM north of Philly, we encountered really nasty conditions in the Delaware bay, heading for Cape May. We held 10+ knots through the bay and then entered the canal. We stayed the night at a marina in Cape May.

We were at the bar that eve and ended up talking to a bunch of sport fisherman who had been out in the bay that afternoon. One of them pointed to his boat, a Viking SF in the high 50 ft range and said, "That's a 35 Knot boat! We couldn't do better than 9 knots out there today, I can't imagine how slow you must have had to go in that Motor Yacht!" I didn't have the heart to tell him that we were going faster than he was! Nothing was displaced or tossed around. The boats are definitely capable of handling whatever!

yachtsmanbill
06-30-2008, 06:21 PM
Thanks Bill,

Whats the hull speed of a 58?


Someone here posted the constant for figuring hull speed, and if I remember correctly, the 58 with the cockpit extension (65 LOA) was around 10.4 mph.
The gps shows a good day on the TennTom around mile 401.
1400 rpm seemed to be around the "sweet spot". ws

krush
06-30-2008, 06:38 PM
a little insight on hull speed: http://www.boatdesign.net/forums/showthread.php?t=1220

Bill, I think I'm just gong to install a boiler and steam engine. We'll just stop every so often to gather wood LOL

Pascal
06-30-2008, 08:00 PM
"Something else just occurred to me...How are 58's in sloppy conditions at 9 knots? These appear to be a bit top heavy (Could be wrong) and perhaps were never intended for life in the slow lane. A MY is not the same as an LRC afterall.

Any 55-60 owners care to comment? Ang??? Freebird???"

head on, they're fine... waves dont' stand a chance against the mass of a 1510. when the seas start coming on the beam, they roll.... probably a little more than other boats with a lower CG like the LRCs. Depending on how you use the boat, it cna be a small trade off for the extra livign space....

hull speed is 1.33 x sq rt LWL on the 53, it's about 9.2kts. when you get close to 9 kts, you're fuel burn goes up... you really feel it just looking at the wake.

the 1510s are more economical at that speed than the wider beam, newer models like 54 and 56.

Passages
06-30-2008, 08:43 PM
OK, so looks like hull speed assuming actual LWL of 52 feet is about 9.5 knots.

Now to Krush for the bonus question. Assuming vessel weight of 61k lbs, WL of 52', how much total hp is needed to provide continuous duty of 9.5 knots.



BTW, there is a calculator over on Boatdiesel.com but you need to be a member to play with it. Any members out there?

Avenger
07-01-2008, 08:30 AM
You could get a detroit series 40 (it's a 4cyl 60 used in metro busses). The 40 series 7.6 and 8.7L is a re-branded Navistar DT466E and DT530E. They may have a 4 cyl version of the 60 in the lineup, but I think you're thinking of the 50 series. All really good engines, BTW.

Drystack, huh? Now think about the look of a 58 with no flybridge and a funnel.... Hmmm, sounds pretty "yacht"-like. :)

Brian Degulis
07-01-2008, 12:49 PM
Those Cummins would be a great choice, but they would cost more than the boat that he wants to put them in! A pair of 6-71's worked just fine for the LRC's and they'll work fine in that boat as well. I bet he can find a fresh pair of 6-71's and get them in the boat and still have only spent $100k for the whole thing!

The Cummins QSB 230s cost me around $15,000 each new. A rebuilt 671 outrite cost me around $13000 and your comparing rebuilt to new. Get past all the BS and look at as a project your going to do and the answer is obvious. You don't tear a boat apart to re power and put T Rex in a smaller version back in. The DDs were great but the operative word is were they are absolute junk compared to what's available today. With new electronic engines you will have a 2 year warranty it will be much quieter and smoother it will burn a lot less fuel parts are current and it can run at any RPM continousily without fear cold burn. As a bonus just think of how happy Al Gore will be!!!!!

Brian

Genesis
07-01-2008, 01:14 PM
If you can get QSBs for $15k new you'd be nuts to put 6-71s in there for $12k each.

Absolutely insane.

There is no comparison between those engines, and folks, I'm a BIG fan of Detroits.

The facts, however, are what they are. The social and fuel aspects of the QSBs are immensely favorable.

If I had the 6-71s and needed to buy kits and heads I might be inclined to rebuild them (myself) but starting with empty engine rooms?

That one's easy.

ThirdHatt
07-01-2008, 01:27 PM
My mistake, I thought the new Cummins QSB's were more like $25k each so just the engines were going to be $50k. That's probably what the boat will cost to buy. At that point, like Passages (the guy actually considering this project) said if it is Detroits for half the price of the Cummins, it's Detroits all the way. If the cost of Detroits is actually anywhere in the ballpark of the new Cummins I agree, no brainer. Cummins all the way. Not sure if the 230hp vs the 280-300hp makes much difference in this application.

krush
07-01-2008, 01:34 PM
The 40 series 7.6 and 8.7L is a re-branded Navistar DT466E and DT530E. They may have a 4 cyl version of the 60 in the lineup, but I think you're thinking of the 50 series. All really good engines, BTW.

Drystack, huh? Now think about the look of a 58 with no flybridge and a funnel.... Hmmm, sounds pretty "yacht"-like. :)

I was thinking the 50 series. I don't know why the heck I said 40--didn't even know a 40 series existed.

If you don't plan on ever really going faster than 10 knots, then getting a smaller engine and running it closer to max output should give you the best fuel burn....but that isn't a huge concern if you plan on only doing 100 hours a year. The engines will rust away before you wear them out.

Re: look of a drystack. Functionality trumps all looks in my book :)

doc g
07-01-2008, 01:34 PM
So what's the fuel burn of the QSB 230's at wot . I assume it is a "B" rated so it can run on the pins all day ??..........Pat

REBrueckner
07-01-2008, 02:02 PM
Fuel spec curves for all the QSB's (including two different QSB 230's) at: (Page 2)

http://marine.cummins.com/attachments/public/marine/Products/Recreational%20Inboard/QSB/QSB%20Spec%20Sheet.pdf

Passages
07-01-2008, 03:20 PM
Thanks for the link Rob.

I was surprised the fuel burn was not less though. 5.7 gph @ 2000 rpm @ 102bhp.

Assuming 10 knot speed, that's just shy of 1 gpkm. Heck, our trusty ole DD's can do that.

doc g
07-01-2008, 04:24 PM
I did the math for my boat also ,using some of Brian DeG's # s for a 61 ' . It appears that if you up prop as Brian did you can get the same fuel economy as a repower down to the Cummins. Brian was burning 14-15 gph,at 10 KN at 1150 rpm with 1271's producing 150 /650 hp. It appears that for the Cummins to produce 150 hp the burn rate would be damn near the same . Of course the 12v71's weigh 5200# each and the QSB's are only 1350# each . Taking 8 1/2 tons out of the boat should yield quite an improvement how much ....is the question . I must be missing something as I thought there should be be a huge difference.........Pat

Boatsb
07-01-2008, 04:45 PM
Another option. At least for the 58TC as there is no hallway between the engines. make it a single screw. Just put the engine in the middle not like the Bird did.

Passages
07-01-2008, 04:55 PM
We'll shucks, maybe this can be the first Hatt with Diesel-Electric.

BTW, single screws scare me, expecially in boats that were not designed for it.

mike41tc
07-01-2008, 05:04 PM
There's probably going to be a keel in the way for a single screw. But you might rig the single engine to drive both trans, and props.
Mike

Boatsb
07-01-2008, 05:21 PM
My 28 Pearson express had 3 molded tubes for the stuffing boxes. The center one was unused.I had twins in it. Since the 58 was mostly a displacement hull I think it would do nice with a single engine and thrusters for maneuvering. The hull from what I have seen would handle it nice. Randy and Steve crossed the gulf on his with the engine off center and I believe he did better than 1 MPG at about 9-10 MPH. Of course the center hall models would not work for this and the conversion to single engine dual drive would probably be a pricey one.

Talking to the people I know with the larger hatts I see the fuel price has slowed them down anyway.

Anyone want to see if Randy wants to convert his TC as a test bed?

yachtsmanbill
07-01-2008, 05:55 PM
The TC with no engines appears to be a pretty nice boat. I'd like to see it in person. For less than 70K there are many possibilities for a repower.
Being realistic, consider a few factoids...
Are ya gonna fish 200 miles offshore where outrunning the weather is a factor? The 58 aint the boat for you.
Single engine? Sure... a 12V149 would slip right in the middle after you pull the 2 centerline fuel tanks (I measured mine) The tank depth is almost 3 feet to the keel.
DE? Better yet with a single plus two electric motors. Plenty of room for that and wing tanks.
Any boat that can make 10-12 mph for coastal cruising would be more than adequate. Face it boys... the days of running balls out on plane are already long gone unless youre Harold Hughes. Even 8 hours to Bimini aint bad, and you dont need to worry about outrunning pirates. 16-92s wouldnt matter there either, so WTF???
Now lets really smoke some shoot... gas turbine electric, or Jacuzzi jet with the two mains aft OR with V drives.
The possibilities are endless, and with a nice boat with no motors at a really fair price in a beat down market and lotsa ambition, you cant lose!
Right now that boat is pretty useless, and accruing storage etc. I'll bet the owner really wants it G-A-W-N. I'd make a 20K offer. Whats he gonna do except turn it down?
"Hittem hard, hittem low and hittem fast" Knute Rockne... ws

Pete
07-01-2008, 06:11 PM
58 LRC's came with both 471 and 671 engines, set up with small injectors. My 48 has 453 rated from the factory at 112 HP. Too small in my opinion for a 58. Also consider that as you drop the horsepower/torque, your skill using both the gears and throttles during docking needs to increase exponentially.

Pete

Brian Degulis
07-01-2008, 08:19 PM
I did the math for my boat also ,using some of Brian DeG's # s for a 61 ' . It appears that if you up prop as Brian did you can get the same fuel economy as a repower down to the Cummins. Brian was burning 14-15 gph,at 10 KN at 1150 rpm with 1271's producing 150 /650 hp. It appears that for the Cummins to produce 150 hp the burn rate would be damn near the same . Of course the 12v71's weigh 5200# each and the QSB's are only 1350# each . Taking 8 1/2 tons out of the boat should yield quite an improvement how much ....is the question . I must be missing something as I thought there should be be a huge difference.........Pat

The fuel savings alone does not justify the cost and the work. But if I were faced with rebuilding the DDs I would make the switch in a heartbeat. I would do the Aqua Drives and add some isulation while I'm at. Run Silent Run Clean Hopefully not to deep.

Brian

krush
07-01-2008, 08:45 PM
Don't forget controllable pitch props. You need them too. http://www.kastenmarine.com/CPprops.htm Cool info.

Diesel electric is cool, but if you can get a controllable pitch prop, you don't need to do all the work to get diesel electric.

Bill, here's what you do. Diesel electric, with twin 800-1000hp motors (or combination of motors). Have 2 or 3 generators of various sizes to run the hotel loads and cruise. Then have a gas turbine (1500-2000hp) to run fast--and burn a ton of fuel. A 1500hp turbo-shaft is light and small.

Brian Degulis
07-01-2008, 09:51 PM
I'm convinced that Diesel Electric and Controlable Pitch Props are no longer of any advantage at all in recreational boats under 125'. All you gained with them was the ability to properly load the engine at any RPM or load conditions. With todays electronic engines there is no longer any benifit to that.

Brian

yachtsmanbill
07-01-2008, 10:07 PM
Don't forget controllable pitch props. You need them too. http://www.kastenmarine.com/CPprops.htm Cool info.

Diesel electric is cool, but if you can get a controllable pitch prop, you don't need to do all the work to get diesel electric.

Bill, here's what you do. Diesel electric, with twin 800-1000hp motors (or combination of motors). Have 2 or 3 generators of various sizes to run the hotel loads and cruise. Then have a gas turbine (1500-2000hp) to run fast--and burn a ton of fuel. A 1500hp turbo-shaft is light and small.


1500 SHP?? Thats kid stuff! I'm talking 10Mw... do the horsepower math on that one. Left over juice would fire up the neighborhood too. Lets see, the boat bussed to a 16 kv breaker, into a 138 kv transformer and onto the grid... now where'd I leave that bowl LOL
Actually lets break into a subject thats new here... My pal is finishing a prototype hydrogen generator for his Ford Clitescort. It runs at 15 amps at 12 vdc. The unit is piped directly into the plenum after the MAF sensor. That 15 amps is supposed to double his mileage. How much generation would you need to offset fuel oil by 100%?? Given a burn rate of say, 20 gallons per hour. I'll try it on the sub with a 20 kw genset. ws

krush
07-01-2008, 10:17 PM
Bill, that entropy thing is a bitch. Taking electrical power (which comes from mechanical power) to make hydrogen doesn't make much sense to me. Can't get something for nothing.

yachtsmanbill
07-01-2008, 10:30 PM
Thats what confuses me too... Lets say 15 amps is 2 horsepower. the amount of gas generated equals 10 HP. I understand entrophysical loss, but it seems that this is a gain instead off the loss. Recapturing heat rate loss perhaps? Just need to get off that stupid ethanol bandwagon. More to follow after the prototype hits the road! ws

MikeP
07-01-2008, 11:07 PM
Dang! I KEEP saying I'm going drag out that perpetual motion machine I bought from a guy in Nigeria some years ago. Wonder if it's still running? Should be, I guess. I keep putting it off because it's behind the stack of 100MPG carburetors and my Cold Fusion generator.

But I think the time is right... ;)

Roscoe
07-02-2008, 01:36 AM
Cummins QSL 9 285 hp @ 1800 rpm continuous rating. Full authority electronic engine.

Roscoe
07-02-2008, 01:50 AM
OK, so looks like hull speed assuming actual LWL of 52 feet is about 9.5 knots.

Now to Krush for the bonus question. Assuming vessel weight of 61k lbs, WL of 52', how much total hp is needed to provide continuous duty of 9.5 knots.



BTW, there is a calculator over on Boatdiesel.com but you need to be a member to play with it. Any members out there?


The calculator shows 128 hp @ 9.8 kts @7gph but that is for 285 hp @ 1800 cruising @ 1100 rpm with 40 x 40 props / 3:1 reduction.

Passages
07-02-2008, 08:25 AM
The calculator shows 128 hp @ 9.8 kts @7gph but that is for 285 hp @ 1800 cruising @ 1100 rpm with 40 x 40 props / 3:1 reduction.

Only 128 hp?
Whoa, I COULD put a pair of 115 hp 4-53's in there.

Or could I?

Brian Degulis
07-02-2008, 09:08 AM
That's the beauty of electronic engines unlike our DDs they have no ideal RPM. You could re power this boat with the same or even more HP than it has now so it could go just as fast. But you would be able to go trawler speed forever with no loss of efficiency and no worries of harming the engine.
When you get past the service manuals and into installation parameters you see the difference. All mechanical engines are intended to be run within a specific RPM and load range most of the time usually 60 to 80% of it's rating. Electronic engines simply don't have that restriction. But the expense of larger engines is a factor and you would also loss the gains that can be had in turning large props slowly.

Brian

REBrueckner
07-02-2008, 09:53 AM
The only way to get high NMPG is to go slower, slower than 10 knots, and to do so with a single engine. Maybe you could get a 58 ft trawler, full displacement hull, to be efficient at 8 knots, but likely that's about an upper limit. And with the Hatteras design, you'll likely be hard pressed to get over 7 knots with any kind of effciency,and that will be compromised by twin screw engines. (Just guessestimated figures on my part.)

For two or three NMPG, you must have single screw, large prop, and more modest cruise speeds that we have been discussing in this thread. Doesn't HP increase roughly as the speed cubed?? We posted that in another discussion earlier this year....if that's the approximate figure, going from say six to eight knots (which doesn't sound like all that much) means HP increases by 8x8x8/6x6x6 or about 237%...so fuel use more than doubles for that two extra knots....

Brian Degulis
07-02-2008, 11:59 AM
That's true if you consider only that and nothing else. If you take this 58' and go for a speed of say 8 kts roughly 150HP is required so 1 200 HP engine will work. In order to get the most out of it you have to use a large prop and a deep reduction. That would be around 45" on at least a 4:1 gear the 58' can't swing that. Even if you re engineered to do it you would have problems with the steep shaft angle and to much draft for a lot of areas. If you went with 2 100 HP engines you could swing the ideal prop with none of those problems. That difference gets you very close to the single engines fuel burn in some cases it's better.

Brian

Passages
07-02-2008, 12:21 PM
Did some more digging on the QSB 230 series.

1200 rpm is all that is needed to produce 106 hp each. The fuel burn is 1.9 gph.

So, 3.8 gph for 9.5 knots? If so, I'm sold on Cummins.

Genesis
07-02-2008, 12:59 PM
That's double what you'd expect to get running 6-71s in displacement mode.

I'd say that's a damn good improvement.

Brian Degulis
07-02-2008, 02:19 PM
Did some more digging on the QSB 230 series.

1200 rpm is all that is needed to produce 106 hp each. The fuel burn is 1.9 gph.

So, 3.8 gph for 9.5 knots? If so, I'm sold on Cummins.

Something is wrong with that calculation I think you might have read the fuel burn off the prop curve and the HP off the engine curve.

Brian

REBrueckner
07-02-2008, 03:07 PM
I agree with Brian...you can't get 106 HP at only 1200 RPM from a 230 HP engine...be more like 50 or 60 HP there....that's just a guess....

My 435HP 8V71TI's produce only about that 110 HP or so at 1500 RPM....


On the other hand, if you can't get 30% or better NMPG with brand new QSM's vs DD I'd also be really surprised....maybe 60% better at eight or so knots cruising....

dsharp
07-02-2008, 04:22 PM
We stretched a 45' double cabin hatteras hull to 51' and installed a pair of inclined 6-71's. We also added two 500 gallon fuel tanks in the middle. The boat would make 10 kts at 1600 and about 13kts at 2100. The boat would plane in shallow water and light on fuel. The boat held 1600 gallons total and burned right at 10 gallons an hour if my memory is correct. The boat had 2.5 to 1 gears and I think the wheels were around 32" square. I don't think you would want any less power in a 58 footer.

Brian Degulis
07-02-2008, 05:43 PM
I agree with Brian...you can't get 106 HP at only 1200 RPM from a 230 HP engine...be more like 50 or 60 HP there....that's just a guess....

My 435HP 8V71TI's produce only about that 110 HP or so at 1500 RPM....


On the other hand, if you can't get 30% or better NMPG with brand new QSM's vs DD I'd also be really surprised....maybe 60% better at eight or so knots cruising....

That's not what's wrong the QSB 230 will produce 100 HP @1200 but not with so little fuel consumption. Your 871TIs will produce around 250HP @ 1500 your probably reading the prop consumption curve which will be much lower than what the engines capable of untill you get to WOT.

Brian

krush
07-02-2008, 10:36 PM
It may not hurt an electronic engine to run it at lower loads, but I'd be very surprised if the brake specific fuel consumption isn't better when you full load the engine.

Passages
07-02-2008, 11:30 PM
That's not what's wrong the QSB 230 will produce 100 HP @1200 but not with so little fuel consumption. Your 871TIs will produce around 250HP @ 1500 your probably reading the prop consumption curve which will be much lower than what the engines capable of untill you get to WOT.

Brian

Hey guys - I'm not making this up. (But I may be reading the table wrong)

http://marine.cummins.com/attachments/public/marine/Products/Recreational%20Inboard/QSB/Fr91370.pdf

Roscoe
07-03-2008, 01:44 AM
It may not hurt an electronic engine to run it at lower loads, but I'd be very surprised if the brake specific fuel consumption isn't better when you full load the engine.


I've analysed the generic prop calculator info and used specific BSFC data for the QSL9 Cummins resulting in improved fuel burn compared to the generic info. The BSFC burn is best under load @ +/- .355 lb/hp or 20 hp/gal while the low cruise rpm results in a fuel burn of .440 lb/hp or 16 hp/gal.

Brian Degulis
07-03-2008, 08:17 AM
Hey guys - I'm not making this up. (But I may be reading the table wrong)

http://marine.cummins.com/attachments/public/marine/Products/Recreational%20Inboard/QSB/Fr91370.pdf

That's a crapy power curve but if you study it a little more you will see that your reading the fuel consumption from the prop curve and the power output from the engine curve. At 1200 RPM on the prop curve the engine is only developing around 40HP that's at a fuel consumtion of 1.9 GPH. Use the graph at the bottom to calculate the fuel consumtion at 1200 RPM developing 100 HP it's the top line. I didn't print it out and do it but it looks like around 5 GPH.

Brian

REBrueckner
07-03-2008, 08:21 AM
Passages: I read those graphs as Brian does....that's what I was trying to say in my earlier post....your quoted HP was much too high at 1200 RPM....

You'll be hard pressed to run a 58 foot Hatteras hull 9.5 knots at trawler efficiencies...maybe at 7 knots you'd be closer...

And Roscoe's post is also enlightening... from .440 to .355 may not sound like much of a change but it is: .440/.355 is 1.239, about at 24% difference in engine efficiency...!!!!!!

So between (a) twin screw losses (smaller props and twin engine) (b) non displacement hull, (c) engine loading, (d) 9 or 10 knot cruise....and you can begin to see the factors making it so very hard to get displacement efficiency....

Brian Degulis
07-03-2008, 08:30 AM
It may not hurt an electronic engine to run it at lower loads, but I'd be very surprised if the brake specific fuel consumption isn't better when you full load the engine.

Your right it is better as power output goes up but the diffrence is so small it's not worth considering. The diffrence on mechanical engines can be 40% I never figured it out on the electronics but I bet it's under 3%. Power and Motoryacht had a big article on this it was called "Facts and Myths of Diesel Electric" it goes into the diffrences between mechanical and electronic engines. BTW All the info I have is on the John Deere 6068 and the Cummins QSB 230 cause that's what we use. So other engines might be diffrent but if they are current with Tier III emissions requirements they should be very close.

Brian

q240z
07-03-2008, 02:31 PM
This whole thread has been very interesting.

I don't post here often because I'm a loyal Chris Crafter, but repowering planing hulls for trawler speed isn't a topic only of interest to Passages and other Hatterii. I've got 6-71Ns in my current Connie and we tend to putz around at 7-9kts most of the time. Last year we acquired a 46' aluminum hulled Roamer that had 534ci twin turbo and intercooled SeaMaster gassers that were frozen solid, we started looking at all of the repower possibilities. I spent a lot of time looking at all other power options out there, including going with 871 power that was originally available in the 46 Roamers in addition to the 427 Fords that were the OE power for my boat. Much as I love my 671s (and I found several pairs that were available at a very reasonable price) I eventually settled on 120hp Lehmans.

I went with Lehmans because I found a good set with TD502 gears for about the price of one 270 Cummins sans gear. The local Lehman guru checked them out and has declared that they've still got 10,000 hours or so left in them as long as I keep the RPMs below 1800 and the fluid changes on schedule. A couple of ragboater buddies are extremely pleased with their little Lehmans. With 50 and 62' hulls, respectively, they claim to pull 2-3gph@9kts. Granted, those are displacement hulls, but I'm hoping they'll prove to be much more efficient than DD power. Quieter, too. Time will tell.

On another note, one thing a Cummins guru mentioned is that Cummins Mercruisers can be problematic. Something about French marinization of the very robust Cummins diesel...I don't recall all of the details, but the advice given was to stay away from Cummins Mercruisers.

Roscoe
07-04-2008, 01:10 AM
Did some more digging on the QSB 230 series.

1200 rpm is all that is needed to produce 106 hp each. The fuel burn is 1.9 gph.

So, 3.8 gph for 9.5 knots? If so, I'm sold on Cummins.


QSB230 @ 1200 produces around 20 hp at the prop @ 1.5 gph.

In my discussions with the pros at boatdiesel, the use of small displacement, high rpm diesels was not recommended for displacement boats. The QSB turns 3,000 rpm and is used with the Mercruiser Bravo sterndrive for go-fast boats.

Passages
07-07-2008, 08:33 AM
Never mind...

My son & I took a ride over to Mystic to see the boat that inspired this thread. Only one word to describe it. "SAD"

If it only needed engines, it might have worked, but this was a job for the likes of Yachtsmanbill.

Shame really.

Oh well, back to option "A".... Buy the best maintained boat I can find and keep it that way.

krush
07-07-2008, 09:45 AM
Oh well, back to option "A".... Buy the best maintained boat I can find and keep it that way.


You really need to consider option B for bayliner or D...for double-wide!

Passages
07-07-2008, 10:13 AM
You really need to consider option B for bayliner or D...for double-wide!
Krush - Go pound some pilings...(:-)

krush
07-07-2008, 10:41 AM
Krush - Go pound some pilings...(:-)

New thread to come shortly.

yachtsmanbill
07-07-2008, 11:01 AM
I know that pics can be very misleading... so what else was so wrong that a 20 K offer wouldnt fix? Aside from Krushs' piles it looked pretty salvageable... ws

Passages
07-07-2008, 11:40 AM
I know that pics can be very misleading... so what else was so wrong that a 20 K offer wouldnt fix? Aside from Krushs' piles it looked pretty salvageable... ws

Well since you asked...

This boat has had an odd history. The ower moved to the midwest about 5 years ago and rented the boat to a livaboard with an option to buy. The livaboard ran into some cash flow problems and stripped the boat to pay bills. The liveaboard then abandoned the boat some months ago and the remote owner is now stuck with the beast.

Exterior -
The hull is in excellent shape but that's where the good news ends.
Half the windows are cracked
Ripped out stantions with open screw holes.
Numerious unfilled screw holes in deck allowing water intrusion
Huge opening in cabin roof where engines were yanked
Topsides need paint badly
Windless missing
I did not even go the the bridge

Interior
"That Hatteras Smell"
Rear deck roof rotten and FUBAR
All soft fabrics, rugs & furniture needed to be dumped
Window leaks at lower helm, galley, forward bunkroom
Missing commode
Galley appliance were rust buckets (Except fridge - that looked good)
Engine room was empty black hole of ugly.
Large sections of side paneling were removed to access something???


Even the salesman was apologetic and said this boat would be best suited for someone who owns a marina and needs a project to keep his employees busy.

YM Willie - If you lived in CT, I think would make a great next project for you. In it's current shape, I bet $20k would take it.

Boatsb
07-07-2008, 11:51 AM
make it 50K and I might take it. I would need the 50K to start to make it live able.

krush
07-07-2008, 11:58 AM
YM Willie - If you lived in CT, I think would make a great next project for you. In it's current shape, I bet $20k would take it.


In this market, I hope you mean slick willie will RECIEVE 20k for taking it :)

Passages
07-07-2008, 12:04 PM
In this market, I hope you mean slick willie will RECIEVE 20k for taking it :)

I seriously think you could dump $300k into the refit and when finished, you'd have a nice $250,ooo boat.

Boatsb called it right.

krush
07-07-2008, 12:09 PM
I seriously think you could dump $300k into the refit and when finished, you'd have a nice $250,ooo boat that would sell today for $150k.


I fixed it for ya.

spartonboat1
07-08-2008, 09:04 PM
Well since you asked...

This boat has had an odd history. The ower moved to the midwest about 5 years ago and rented the boat to a livaboard with an option to buy. The livaboard ran into some cash flow problems and stripped the boat to pay bills. The liveaboard then abandoned the boat some months ago and the remote owner is now stuck with the beast.

Exterior -
The hull is in excellent shape but that's where the good news ends.
Half the windows are cracked
Ripped out stantions with open screw holes.
Numerious unfilled screw holes in deck allowing water intrusion
Huge opening in cabin roof where engines were yanked
Topsides need paint badly
Windless missing
I did not even go the the bridge

Interior
"That Hatteras Smell"
Rear deck roof rotten and FUBAR
All soft fabrics, rugs & furniture needed to be dumped
Window leaks at lower helm, galley, forward bunkroom
Missing commode
Galley appliance were rust buckets (Except fridge - that looked good)
Engine room was empty black hole of ugly.
Large sections of side paneling were removed to access something???


Even the salesman was apologetic and said this boat would be best suited for someone who owns a marina and needs a project to keep his employees busy.

YM Willie - If you lived in CT, I think would make a great next project for you. In it's current shape, I bet $20k would take it.
A $1 boat and I'm not being obnoxious. Just a fact of life, if you evaluate the current state and required repairs. If you pay a yard, you better have an 8" x 10" check book for "big" checks. Frankly, a survey is clearly indicated of hull and electrical systems, esp. if out of water.

Walter P
07-08-2008, 10:00 PM
Run.... Do NOT walk away from it.

As was previously stated by Krush, after spending 300 grand you will have a boat worth maybe 250 K, that might sell for 150.

There are so many great deals to be had today that you don't need to get involved in a major headache.

Walt

34Hatt
07-09-2008, 08:38 AM
Good move to walk away Jim you don't need or have time now to take that on!!! Unless you just want to throw money away ;) Then just tow it across the pond and Ill fix it for ya! :)