I came across a gorgeous old 71 Hatteras. It is equipped with 2, DD12v71 normally aspirated diesels putting out 500HP each.
It is stated that the engines both have 3000 hrs of service.
I have been trying to learn about this engine and how many hrs. of life it can go between rebuilds or replacement. Most articles review the turbo charged engine. These seem to go about 5000 hrs.
The natural engines are mentioned as going MUCH longer between rebuild/replacement.
Any body here have experience with this engine?

I had the DD8V engine in my 40' Bluebird motorhome. It is a two cycle engine used in a lot of fire trucks and other applications and was a good performer for me, over 100,000 miles with no problems. It is a strong performer but likes the fuel. Oil, filters, and regular maintenance is the key. Other than those comments I can't think of any major issues and perhaps someone on the forum may have further comments. Good Luck with your boat. The Hatteras is a beautiful yacht.

If you don't find any info anywhere else you can check out heavyequipmentforums.com.

There are a mechanics and guys familiar with these engines that post over there.

We rebuilt (in frame/top end) our 16-71's at 10,000 hours on a small research ship I once ran. They can't make engines like that anymore due to MARPOL air pollution regulations. I think 40,000 hours was the interval for the full rebuild. Ours were 1800 RPM engines.

I own a Yacht Management business in Fort Lauderdale and have been dealing with Detroit Diesels for 25 years. I've run 1000s of them and several hundred Hatteras' and am an Approved Captain for Hatteras yachts and have been for about 12 years. The 71' Hatteras is a good boat. To answer your question
12v71 TI's go 5,000-6,000 hours.

12v71 N's or naturals will go 10,000-12,000 hours in a yacht application usually if not more before rebuilding them. The N's still have a blower, but no turbo's. Chances are you won't even get close to putting 7,000 hours on them in your lifetime. They're good motors. Not as refined as the newer diesels, they leak oil, smoke on start up, but will always run. If you buy the boat, have the rack set and valves adjusted and then just keep up with oil changes, zincs, fuel filters (a biggie), and raw water impellors. I'd have a mechanic open up the air boxes and look at the piston liners (you can inspect them on a Detroit just by taking the air box inspection ports off (2 bolts for each one)and check them out. But Hatteras is the best built boat and Detroits are the best motors for the era you are looking at.

I see you're in Chicago. I did the entire Great Loop in 2008 in a 1988 75' Hatteras MY and it sat at Burnham Harbor Marina for the summer of 2008. If the boat is older than 1987 it's going to be a 32 volt DC boat, newer 24 volt DC (which is the current stuff), you can find 32 volt DC parts but it's harder to find.

If you have any questions on either the boat or the engines email me at anytime and just put "hatteras" in the subject line.

a good forum for questions is yachtforums.

In that boat I do not believe they are rated for 500 hp. I overhauled a pair of twin turbo 8-71's, I recall that they were rated at 450 hp.

Usually these go 4,000 hours then need an in-frame overhaul. Basically a piston and liner job, plus bearings and heads rebuilt. You can do this again at 8,000 hours, but at 12,000 hours the motors need to come out and receive a complete rebuild.

Parts are relatively low cost. When I did two of then in a 53' Hatteras it took me a month, from what I remember. However it could have been longer. I had a helper for some of the work. Everything is heavy, even the oil pan weighed about 100 lbs.

At the size of the investment you're about to make, hiring an experienced marine and (separate) DD engine surveyor is a no-brainer and well worth the cost. Gives you leverage on the price or the knowledge to walk away before you make a bad deal.

As an aside, I love the sound of the old detroits.

Edit to add: Even if you have to pay to fly in a surveyor from Florida or the East coast, it's still worth the money.

quote:

Originally posted by dkjbama:
At the size of the investment you're about to make, hiring an experienced marine and (separate) DD engine surveyor is a no-brainer and well worth the cost. Gives you leverage on the price or the knowledge to walk away before you make a bad deal.

As an aside, I love the sound of the old detroits.

Edit to add: Even if you have to pay to fly in a surveyor from Florida or the East coast, it's still worth the money.

I'm assuming you will have a Marine Surveyor inspect the entire boat prior to purchase. Because of the age your finance source (unless you are paying cash) and insurance company may require it anyway.

The surveyor will be able to give you good information on the entire propulsion system.

quote:

Originally posted by c1steve:
In that boat I do not believe they are rated for 500 hp. I overhauled a pair of twin turbo 8-71's, I recall that they were rated at 450 hp.

Usually these go 4,000 hours then need an in-frame overhaul. Basically a piston and liner job, plus bearings and heads rebuilt. You can do this again at 8,000 hours, but at 12,000 hours the motors need to come out and receive a complete rebuild.

Parts are relatively low cost. When I did two of then in a 53' Hatteras it took me a month, from what I remember. However it could have been longer. I had a helper for some of the work. Everything is heavy, even the oil pan weighed about 100 lbs.

Naturals go a lot longer than the turbo charged versions. You should not need to pull the heads off for any reason till you have to do a major on them....which should be a minimum of 10,000 hours or more on a properly taken care of 12v71N. 500 HP seems like a realistic number and again it depends what injectors they have in them....N80's N110's.....what company marinized them and spec'ed the injectors....etc. I too highly recommend a hull surveyor and an engine surveyor (or just a good DD marine mechanic). Keep in mind annual maintenance on a boat like this is pretty hefty.

I love the sound of a 2 stroke Detroit. I don't know about marine applications, but in semi trucks, you ran them like you hated them, spooled up all the time. Drop in a gallon of oil every other day to replace what it slobers all over the bottom of the truck. Never run it out of fuel. It practically requires a mechanic to get one to re-prime.

Do boats have an emergency runaway butterfly in the air intake? Sometimes in older equipment those aren't working. Always nice to have a way to stop one when it decides it's going to go wide open.

From what I remember they all did. There was a chrome T-handle up in the control station that led to the butterfly at the air intake.

I love the way they sound, but working on them always scared me a bit. I know a fishing boat deck hand who decided to adjust the valves on a very recently rebuilt DD. He left one of the locknuts not fully tight. Half an hour later the engine threw a connecting rod through the side of the block. I was always careful working on them, super super careful.

Thanks for all the advice.
I'm not even close to buying this boat. I stumbled upon it and was taken back by its old school Beauty and charm. Its a 58' tri cabin, on Lake Michigan ( a google search brings it right up).
My mechanic got me looking after he raved about summer life at the marina and his boat. I thought a floating vacation house on the lake that my wife and I and my son and his wife could spend weekends on or longer. An occasional trip to Michigan or around the great lakes would be nice when I retire.
I just read yesterday about the circle trips, that would be a fantastic, relaxing cruise, maybe winter in Florida or the Gulf.
I was worried that this boat would be too big for river cruising and I need to check the height restriction to clear the feared bridge outside Chicago.

I'm a boat virgin but I have been around engines and mechanics all my life. I do all the maintenance on My 40' Foretravel motor home and the Cummings M11 diesel and Allison 4060 trans. Heavy work I would have to have done but normal maintenance I can handle.
Because of my ignorance of boats and the complexity of the boat,I had planned on paying a captain for instruction to bring me up to speed and confidence if I decide to go further. A Marine surveyor would most definitely be retained. I would need a mechanical inspection, a bad engine or major work would be a deal breaker. From what I have read, a in place rebuild (not recommended} would be over $50,000 and a replacement of both engines would be well over $80,000. It obviously would be a catastrophic expense. If I can use the boat and maintain it and still have life left in the power train I would probably sell it in a few years. I would not finance this boat.
A 1971 boat does scare me,my mechanical side is screaming at me to forget it, my nostalgic, romantic side is screaming "go for it".
We all have been there.

You're getting bad information.

ALL marine diesels are majored (rebuilt) in place unless you absolutely have to remove the engine from the boat. There's no issue doing a major in place. A major on a 12v71N should be $40k, in place, you have no turbo's to rebuild, intercoolers to clean or aftercoolers......perhaps even less.

Like I said earlier, I did the ENTIRE Great Loop in a 75' Hatteras MY. I found it online, the arch should be hinged. With the arch and bimini top down, you will clear the Chicago bridges no problem (they're 19'2) this is past Chicago and there's more than 1. East Coast (Erie Canal) from Oswego to NYC is 20'6 minimum clearance. On the 65' Hatteras MY turned into a 75' MY with a cockpit extension, our height was down to 18'6 with the arch and bimini down. Arch comes down relatively easy with a couple of guys.....tie a rope to it and put a few wraps on the helm chair base, pull 2 pins and slowly let it come down.

The boat does have a lot of nice, expensive add-ons (if they work) stabilizers, bow thruster, vaccuflush toilets etc.

Keep in mind maintaining a boat that size is expensive. Maintenance on the engines shouldn't be a big deal. Most of the systems aren't too much of a big deal either......access is good to most items. Hatteras used copper lines for the fuel and water systems on those years and fiberglass fuel and water tanks which should all be fine. The age is no issue provided there is no rot in the decks as Hatteras used Balsa wood as the coring on the decks in this era. The same stuff breaks on a 1971 boat as it does on a 2007 boat. The Hatteras of that era were built like a tank.

Yes, all Hatteras have the T-handle pull cable shut off's for the detroit diesel emergency shutdown air damper flaps at the lower helm, problem is nobody ever works them because they don't want to go to the engine room and reset them and the cable are usually frozen and useless.

Armored, I work a 4 week on/4 week off schedule, so if you do desire someone to provide some instruction I have some availability, My wife is from MI and we visit fairly often. If you decide to take the plunge I'm sure we could work something out. I am mostly a big ship captain, but I have circumnavigated on a 40' ketch, and am a qualified powerboat instructor at Chapman's so I can probably teach you some useful skills and get you pointed in the right direction.

You guys are the best. I will contact both of you if I continue on with this.

quote:

Originally posted by jimmy123x:
Yes, all Hatteras have the T-handle pull cable shut off's for the detroit diesel emergency shutdown air damper flaps at the lower helm, problem is nobody ever works them because they don't want to go to the engine room and reset them and the cable are usually frozen and useless.

In that case, let's hope the bow is pointed towards open water when it decides to go a galloping, lol. In a truck with a manual transmission you could always wrestle it to a stop with the brakes. I once had my brother's 1980 VW Rabbit run away. Exciting ride.

quote:

Originally posted by sigcrazy7:

quote:

Originally posted by jimmy123x:
Yes, all Hatteras have the T-handle pull cable shut off's for the detroit diesel emergency shutdown air damper flaps at the lower helm, problem is nobody ever works them because they don't want to go to the engine room and reset them and the cable are usually frozen and useless.

In that case, let's hope the bow is pointed towards open water when it decides to go a galloping, lol. In a truck with a manual transmission you could always wrestle it to a stop with the brakes. I once had my brother's 1980 VW Rabbit run away. Exciting ride.

You can put the engine in neutral and it will rev until parts start flying. If you're in the vicinity of the engine room you could shut off the fuel supply, almost all yachts have valves to do this.

I've heard of run away diesels, know mechanics that have had it happen to them, don't know of any Captains that have had it happen. An owner had it happen on his generator, the governor wore apart, and it started producing like 300-400 volts!!!!!!

A lot of times or most of the time, runaways occur right after the rack was set or valves were set and is a screw up from the mechanic and it happens within minutes of the engine being started for the mechanic. In all the years and 100,000s of miles that I've run yachts, I've never had one happen to me. I have had about 12 different electronic control failures with the engines going in gear, or not going in gear, or accelerating all on their own over the years.

How does the power transfer from the engines to the propeller shafts?
Is this something that requires constant attention?
What kind of life expectancy is there for this component.

Thanks.

I have had great luck with these:
http://www.twindisc.com/marine...ducts/transmissions/

They are low maintenance and should last the life of the vessel.

The runaways I have seen are due to oil buildup in the intake. If it builds up enough to start pulling it in, then off it goes until it has finished burning the oil. Shutting down the fuel won't stop it because it is burning oil. Perhaps in yachts the intakes are different so they don't pool oil like a DD in a truck or bus.

If a truck was out of gear and started to run away, the only thing you could do was run away and watch as the truck came apart. Assuming the emergency cut off was not functioning.

I'm surprised at the prices for a full inframe. Is it just a yacht thing, or is it because the engine is a 12v71? Or is the $40K price tag for both engines? The last time we had to do an 8v71, it was very cheap.