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Old 17-09-2013, 19:19   #31
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re: Detroit Diesel Question?

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ok, maybe that's why, because it was at idle. The engine room also seemed well insulated.
DD engines sound quite nice at idle , rev them up and they are screaming banshees with all that blower noise i once helped repair one on a water well drilling rig , wow was it loud when it was working hard

dave
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Old 18-09-2013, 05:55   #32
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re: Detroit Diesel Question?

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DD engines sound quite nice at idle , rev them up and they are screaming banshees with all that blower noise i once helped repair one on a water well drilling rig , wow was it loud when it was working hard

dave

Ok, well that's good to know. Seems most of the 80's MYs have them.
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Old 18-09-2013, 06:23   #33
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re: Detroit Diesel Question?

The key to longevity in a Detroit is the HP rating. They make several different versions of the 12-71 at different HP ratings. The higher the HP the shorter the life of the engine before needing a rebuild. If a broker or owner tries to convince you that a high performance Detroit 12-71 is an upgrade, they are full of BS. Look for the ones with the smaller injectors at lower HP ratings.
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Old 18-09-2013, 07:58   #34
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re: Detroit Diesel Question?

I love my 8/71. I also love my 63 ft steel trawler.
The ugly truth about sailboats is that they almost never sail. For the four days a year a cruising sailboat actually sails somewhere, the cruisers spend 361 days in a tight coffin shaped box with a stick on it. Every little piece of hardware or whatever is ridiculously expensive and hard to come by. I rebuilt my trawler straight out of Home Depot, the systems are simple and easy to get to.
Many on this forum suggested that a boat this size was way too much for a retired couple to handle and maintain. That was five years and 10,000 miles ago.
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Old 20-09-2013, 10:38   #35
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re: Detroit Diesel Question?

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The key to longevity in a Detroit is the HP rating. They make several different versions of the 12-71 at different HP ratings. The higher the HP the shorter the life of the engine before needing a rebuild. If a broker or owner tries to convince you that a high performance Detroit 12-71 is an upgrade, they are full of BS. Look for the ones with the smaller injectors at lower HP ratings.
Capt Alex, thanks for your input.

What is a good horsepower in your opinion? 650?
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Old 20-09-2013, 10:52   #36
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Re: Detroit Diesel Question?

What do you guys think?

How many hours before DD's need to be overhauled? (I realize that there are many factors to consider, just looking for a general idea)

Someone told me that it runs about 10-12 grand per engine for a DD overall, does this sound fairly accurate?

Thanks everyone for all of your responses, very helpful!!!
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Old 20-09-2013, 11:07   #37
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Re: Detroit Diesel Question?

GG,

Many moons ago I owned a trucking company and here is what I found for the diesels of that era (1970's~1980's).

Detroit Diesel least expensive to spec for a new truck, poorest fuel mileage and around 300K miles to overhaul via oil analysis.

Cummings mid priced to spec, mid range on fuel burn, 500K miles to overhaul.

Cat, most expensive to spec, best fuel efficiency, and I don't know the life for overhaul as the only Cat I had went 750K miles and still didn't need a overhaul.


Times have changed now, DD has the 60 series 4 strokes, Cummings has a family of smaller displacement 5.9 L L-six engines, and I'm not up to date on current Cat offerings, and most on this forum can tell you about Yanmar.

I would guess if a boat was spec'ed with Cats, they probably went high end on the other systems too.
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Old 20-09-2013, 11:21   #38
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Re: Detroit Diesel Question?

650 HP is very conservative for a turbo charged 12-71. I suspect that is a very long lived package. Of course, it all depends on how it was operated and maintained. I can recommend a DD expert in S. FL that does detailed engine surveys. A survey is the only way to know the actual condition and life expectancy of any particular engine. Good luck!
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Old 20-09-2013, 11:28   #39
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Re: Detroit Diesel Question?

A great article on the subject. Also, this web site has some excellent reviews of older Hatteras yachts.
Marine Engines - Comparing Diesel Types: Two Cycle, Four Cycle
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Old 20-09-2013, 12:18   #40
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Re: Detroit Diesel Question?

The DD can run 10,0000+ hours but a lot depends on how maintained, and loading. I would question hours above 5,000 as that is a lot of hours for a boat engine. A natural with small injectors will tend to out live a turbo engines with large injectors, and slow rpm and no load can cause cylinder to glazing. When you ask for the engines to be started, make sure they are cold, and stand at the back to see what comes out of the exhaust. By the color, black, white, grey, none and if there is sheen on the water and how quickly they change/go away. You can get an indication. I would estimate 1 to 2 grand per cylinder. The first thing I do after starting the engines is run to the stern as there should be no smoke and/or sheen

650 hp is high if you plan on going hull speed. The Eagle single 671 is 165 hp. So it depends on how you plan on running/using it. With 650 hp you would probable want to run over hull speed to get up to temp. Most bigger boats do no actually get up on plane over their bow wake, and they dig a huge hole/wake. You will probable get a lot of middle finger waves.
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Old 20-09-2013, 14:13   #41
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Re: Detroit Diesel Question?

A lot depends on how you plan to use your trawler. If you live on it full time, you will love the space and comfort, and if you travel less than 1000 miles a year the cost of fuel will be about a gallon a mile. We never use marinas, as they tend to be expensive for a large boat, and we don't need their electric power, water, showers, or washing machines. As for your question about engine life, it is very doubtful you will ever put enough hours on your diesel to affect it. In any case, it will cost you less than 10k to totally rebuild a 12/71.
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Old 20-09-2013, 16:28   #42
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Re: Detroit Diesel Question?

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650 HP is very conservative for a turbo charged 12-71. I suspect that is a very long lived package. Of course, it all depends on how it was operated and maintained. I can recommend a DD expert in S. FL that does detailed engine surveys. A survey is the only way to know the actual condition and life expectancy of any particular engine. Good luck!
Ok. I would like your recommendation please. Thank you.
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Old 20-09-2013, 16:49   #43
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Re: Detroit Diesel Question?

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A great article on the subject. Also, this web site has some excellent reviews of older Hatteras yachts.
Marine Engines - Comparing Diesel Types: Two Cycle, Four Cycle
Thanks Capt. I read it, but none the wiser I think I need "Diesels for Dummies"
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Old 20-09-2013, 20:48   #44
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Re: Detroit Diesel Question?

I have run 12V-71's since the late 70's.
I have NEVER seen a 71 series start backwards and suck all the oil out of the base and run away and I bet I have 40,000 hrs running them.
I have had N series, TI's and TA's.
The 480 hp N series with N-70 injectors are bullet proof.
The 650-750 hp TI engines with hot turbos are becoming very dated.
I owned a 900 HP 12V-71TA 7122-7600 build set up and it was the finest engine I have ever owned.

But, compared to 4 stroke engines, they simply love fuel.
The quality of parts is also becoming an issue, not so much pistons, liners and bearing, but reman injectors, turbos, and blowers are not what they once were, and since MTU took over Detroit, the parts for the 2 stroke engines are alot higher than they once were.

But all that being said, all I can say about them is what Capt Omie said about them.

" I love those Vee 12's, don't you? "

The TI engines are of an age that the intercoolers are worn out and they are very high to replace.

As much as it pains me to say, I would look for something with slow turning Cummins or Cats for economy and long life.

In their day, they were the finest engines on earth, but their day is nearly done. And it pains me to say that.
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Old 20-09-2013, 23:35   #45
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Re: Detroit Diesel Question?

GG , I hate to say it, cus Ima Detroit lover and owner. But unless ya want to live down here in Louisiana, they are real expensive to maintain, love to use fuel, and parts are getting harder to find, cus a lot of the parts have ended up down here!! The 12-71 is a fine engine, IF it's been maintained!! Theres many, many of them of these engines running in larger shrimp boats down here! and most of the owners would never change as long as parts and service is available! BUT if it were I, I would be searching for boats with different engines, cats if ya can !! There out there, and don't be in a hurry, better to look a little more, and be happier, and have something you will be able to sell down the line!!! Just my 2 cents
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