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anglermgt
09-15-2008, 08:27 AM
i am looking forward to becoming a new used hatt owner.
i have a 58 tri cabin i am looking at. it has DD 12v71 naturals
displacement is 63000
cruise speed is 15 knts and 19 at top speed as told by broker
i will be traveling to central america from FLA so fuel consumption is issue
QUESTION: how much fuel does each motor use at cruise and top speed for such a heavy vessel?
motors have 850hrs after in place rebuild. told they run like a champ no smoke, both get to full rpm. owner was not there to run motors so this will be double checked by yacht survey co.
QUESTION: how many hours till you need to rebuild on average?
QUESTION:is there any other concerns to look for atypical for hatts?
all other features inside vessel all work.
it is a 1975 58' tri cabin for 120k. comparing prices this seems to be a good deal. which makes me wonder.....
thanks in advance, Drew

yachtsmanbill
09-15-2008, 08:43 AM
My 1974 58TC with 12-71Ns burns 16 gph at 1400 rpm at 11 mph. Tankage is advertised at 950 gallons , so at a 600 usable range that should net you about 37 hours of run time or about 400+ miles. ws

Sparky1
09-15-2008, 11:33 AM
According to the owner's manual supplied by Hatteras, the 58TC has a capacity of 850 usable gallons. If you're the adventurous type, remove a prop and run on one engine. 1,400 rpm will get you about 9mph depending on conditions and net you about 1.3 statute mpg. That will save you a ton of money and extend your range considerably.

Brian Degulis
09-15-2008, 11:43 AM
Or you could remove both props and you won't use any fuel at all!!!!

Brian

garyd
09-15-2008, 12:33 PM
And while your at it. You might as well remove both engines and add a sail and wind generator. Who said you can't run these hatts eccomically?

garyd

Passages
09-15-2008, 12:55 PM
If you're the adventurous type, remove a prop and run on one engine. 1,400 rpm will get you about 9mph depending on conditions and net you about 1.3 statute mpg. That will save you a ton of money and extend your range considerably.

I can't imagine any sane person ever doing that.

Sparky1
09-15-2008, 01:02 PM
Sanity is over-rated.

Seriously guys, I was just trying to give some useful information to this gentleman which may prove helpful. I can honestly say that if I had such a trip in front of me (again) with fuel prices where they are, I would in fact run that boat on one engine. I would certainly keep an eye on the weather and be prepared to re-install it if it were warranted.

Some have claimed there is very little benefit in running on a single engine, but facts are facts. Look at yachtsmanbill's numbers compared to the ones I posted which are very much legit. Either way, good luck on your purchase of that 58. Oh yeah, check the oil lines very closely before you leave the dock.

67hat34c
09-15-2008, 02:01 PM
Running the 58tc on one engine with one prop worked ok but was difficult to stear. Believe the removeal of the prop did reduce enough drag to allow the other engine to run efficiently.

I still think freebird would work will with no engines or tanks and take the center section and fit with multi oars and have topless women rowing. They would have to pay to join the "health club" get a ton of excercise. There will be plenty of food in the fridge for them of course the one pack of lunch meat may be a little old now.

Boatsb
09-15-2008, 02:06 PM
Pull out one engine and re locate the second one in the center. I am sure with a 1271N in th ecenter the boat will perform OK and would steer better.

I will take the women and oars as my smaller boat would be easier for them to row and I have a reputation for topless women on the boat anyway.

Sparky1
09-15-2008, 02:37 PM
Come on guys, be serious. If ever there was a good test of twin vs single on a 58TC, this is it. Bill and I ran the exact stretch of water with the same exact boats and engine(s), and the results speak for themselves.

That being said, I don't know that I would recommend someone new to handling a larger boat with only one engine try this. A lot will depend on how many tight spots he'll have to get in and out of along with how handy he is with spring lines.

One final thought. Bill's boat has a cockpit extension which neither my 58 nor this fellow's will have. I'm sure that would skew the numbers a little, but not that much.

Pascal
09-15-2008, 03:02 PM
seriously, it's all about speed. 15kts cruise is NEVER to going to be economical with a 58 footer, i hope someone gives you a real answer but you cna probably count on about 50GPH giving you a range of 250NM... :-(

slow it down to 9 kts and you will get down to about 12HPG. throttle back some more to 8kts and you shoudl be close to 9 gph or 1NMPG and 700 to 800 miles range.

BIG difference.

yes, pulling a prop will give you a little better economy but i dont' think it's worth it... forget re installing the prop off shore if you have a problem.

depending on how you will use the boat, take a look at the 58YF... the TriC is a good boat but it is not the ground breaking, trend settting classic flush deck motoryacht... it dropped out of production in the mid 70s I think whereas the 53/58 MY YF etc... remained in production with littlle changes all the way into the 90s.

Sparky1
09-15-2008, 03:15 PM
These figures came directly from Detroit Diesel.

12V71N Burn Rate x 2

1200 RPM = 12 GPH
1300 RPM = 14 GPH
1400 RPM = 16 GPH
1500 RPM = 18 GPH
1600 RPM = 19 GPH
1700 RPM = 24 GPH
1800 RPM = 28 GPH
1900 RPM = 32 GPH
2000 RPM = 36 GPH
2100 RPM = 42 GPH
2200 RPM = 48 GPH
2300 RPM = 56 GPH

Sparky1
09-15-2008, 03:35 PM
Maybe this link will help as I used it to calculate speed vs MPG when I bought my 58TC. You will note the GPH figures for the 8V71TI's @ less than 2,000 RPM are very close to the 12V71N's. Given the weight difference between the 53ED and the 58TC, the speeds are also very close.

My 58 ran 18mph @ 2,100 on GPS and topped out at 21mph @ 2,300 RPM. I have a full chart of speeds vs rpm on the boat, but these two figures I remember well.

http://www.hatterasowners.com/Brochures/53ED/53EDA-0083.htm

ThirdHatt
09-15-2008, 03:54 PM
While it is incredible to think of such a journey on one engine in a twin screw boat, I would think that even the adventurous types would probably not do that by choice. Anglermgt is new here and may not know that Sparky was in a very tough situation that lead to his adventure. He was rebuilding one of his 12V71N's and while it was still apart he had to deal with an un-cooperative insurance agent that basically forced him to take the now legendary trip from FL to TN on one engine. Now it has been proven that it can be done when or if it has to, but not necessarily the preferred way to run such a vessel.

Bill burned 16gph running both engines at 11mph but if he slowed down to 8mph like Sparky ran with one engine, the fuel burn would be very close I bet. Running both engines at lower rpm will net similar savings yet with twice the reliability, safety and maneuverability. Beyond that there are options for prop and even gear changes that can help to run a boat slowly and with more efficiently therefore burning less fuel.

Anglermgt, I would look at the planned route and distances between fuel stops for your trip from FL to Central America. Some of the legs may be so long as to need a fuel bladder in addition to running at hull speed or below, other legs may be short enough to run on plane to save time if fuel prices are not a concern (like Venezuela).

GOOD LUCK with the purchase and the journey!!!

captddis
09-15-2008, 04:10 PM
While not quite the same, I ran my 46 1300 mi on one engine with the other prop removed. Had no choice as the stbd engine had 3 spun mains and was unusable. Running one of the 650 hp 8V92s @ 1200 gave 8.4 kts and burned 7gph including generator. I will also add that there was no slobbering and after 160 hr at 1200 rpm there was only a few seconds of smoke when I did run it up. It did 13++ kts on one engine!

Sparky1
09-15-2008, 04:29 PM
For the sake of accuracy, 1,400 RPM on a single engine yielded a speed of 9.6MPH to be exact. I don't think it's recommended to run a 12V71N or any other two stroke DD at less than 1,300 RPM for extended periods of time.

One interesting note in comparing figures listed on the link to the 53ED with 8V71TI's, the props on that test boat were 28 x 31 while Hatteras equipped the 12V71N powered 58TC with 28 x 32 using the same 2:1 Allison transmission.

According to the test data, the 53 achieved 10.4 MPG at 1,300 RPM while using 11.6 GPH. This yielded .9 MPG. Cruising 1,300 RPM with 12V71N's would be approximately 14 GPH with possibly a bit higher speed and about .75 MPG. With these figures in mind, I doubt very seriously that Bill running both engines at a lower RPM level would net anywhere near the 1.3MPG I achieved with the single engine which was very happy running at 1,400. Considering the idle speed of a 12V71N, it would be hard to argue that running both engines at idle speed will not double the GPH of running just one.

Just food for thought, but again, I wouldn't hesitate to repeat the run I made on a single engine. I would bet anglermgt wouldn't have to negotiate some 17 locks en route to South America, and I would also be he wouldn't make the trip alone. :)

ThirdHatt
09-15-2008, 05:49 PM
These figures came directly from Detroit Diesel.

12V71N Burn Rate x 2

1200 RPM = 12 GPH
1300 RPM = 14 GPH
1400 RPM = 16 GPH
1500 RPM = 18 GPH
1600 RPM = 19 GPH
1700 RPM = 24 GPH
1800 RPM = 28 GPH
1900 RPM = 32 GPH
2000 RPM = 36 GPH
2100 RPM = 42 GPH
2200 RPM = 48 GPH
2300 RPM = 56 GPH


Are any specs shown on the curve for 800-1100rpm? My point was just that running both engines at somewhere between 800-1000rpm may just equal the burn rate of one at 1400rpm and still have the option of planing to outrun a storm which could come in quite handy. That security blanket may be worth a few tenths of a mpg to a new owner of an old boat.

Detroits do like to run at high RPM's as has been discussed here at length. The consensus is to simply run them at high rpm for a short period after long periods of running at low rpm's and they'll be just fine. Also, the naturals tolerate low rpm running for extended periods better than the turbocharged versions.

Anglermgt was inquiring about fuel burn at 15kts (32gph) and top speed (56gph), so if we can get him to run hull speed I think he'll be so pleased with the mere 12-14gph total fuel burn compared to running on plane that I bet he'll still use both engines and props, but that's just a guess.

Brian Degulis
09-15-2008, 06:25 PM
Or you could consider a laser beam transporter drive to turn both shafts with one engine. Of course before atempting that you would need to remove both props.

Brian

yachtsmanbill
09-15-2008, 06:32 PM
Run those 12s on Dylithium crystals Sparky !! Warp factor 7 Mr Sulu!! ws

Boatsb
09-15-2008, 06:41 PM
Just hire Sparky's boat transport. They have people experienced at running the single engine route.

In all seriousness the idea of running with a prop removed takes the safety factor away. For a long trip I would look at the slow speed 2 engine routs that gives the option to jump on plane if the need arises. Fuel capacity may be an issue but the bladder tank or a few 55 gallon drums could be added for the long crossings.

I did a long run on my 1960 pacemaker with 4 35 gallon fuel containers and a transfer pump ( manual ) once. After that trip I added 2 additional 50 gal tanks to the boat because the original capacity was not enough for fishing trips beyond 45 miles. If a fuel bladder is only needed a few times it makes sense. If the capacity will not be enough o n a regular basis add permanent tanks.

Sparky1
09-15-2008, 08:56 PM
Run those 12s on Dylithium crystals Sparky !! Warp factor 7 Mr Sulu!! wsSpeaking of Mister Sulu, I saw where he snagged himself a husband. Talk about warped.

You guys talk about safety, which is safer... extending your range by 50% or more or carrying drums of fuel onboard a boat with no cockpit?

I'll drive that boat to Venezuela on one engine for just expenses. I've been promising Miguel I'd come visit.

Boatsb
09-15-2008, 09:14 PM
I like the extra fuel in drums. Below deck ( maybe the best place to put them is down low in the staterooms) and run a transfer hose to the tanks in the boat for filling. No need to go on deck and keep he weight low.

I wish I could go along for the ride but I need to work to pay for my toys or I will lose them.

yachtsmanbill
09-15-2008, 09:15 PM
That 12-71 is back on in OOOLATEWAH or wherever again. $3K Doesent Miguel need one too? Hmmm ws

Sparky1
09-15-2008, 09:31 PM
Miguel has already had his rebuilt and is on vacation in Spain on a big sailboat. I don't want to be buying another engine until I know for sure what mine needs. One way or the other, I'll have that thing running sometime this winter.