Detroit Diesel 12v71's

Pistons and depending on the tune, sometimes cam timing is different from the naturals.
We run the 12V71TIs, 650 hp tune, in a 58 Bert. Do 14 to 20 hour rides coming back from the Bahamas at fast idle. Just like CaptJ said, slowly bring them up every 6 hours and before you have to come in an inlet. Then you will appreciate not detuning them. I've tried one engine at a time thinking to keep one engines temp up would be more efficient than running two cold motors. Naw, another big pain, nil returns.
Stay stock, keep you foot out of them. Open them up once in a while. They will last longer than you.
71s rule.
,RC

If your doing better than 2 gal per mile at 8/10 knots then smile. If your burning more, slow down more.
,rc

Hey Aircar, Are you still on the Forums? I would like to know if you still have your 61? And your experience with it since '08? I am considering an older 61, and would like some advice. Many thanks, Randy Oehmig Crystal River, FL

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Aircar, how many hours do you have on the 61 MY? I am searching for one now. Did the engines survey well? Any former rebuilds on either engine? Thanks.
Capt Michael Email Removed

The OP made 11 posts in 5 yrs of membership, he has made none in the last 3 yrs so don't hold your breath for an answer.

I've been running 71 series since the early 60s. In the military, for others and myself. I always get more hours between overhauls and better fuel economy. A turbo 71 series will get 3000 hours between overhauls with a hired captain or heavy handed owner. A turbo gets more hp out of the same block and heads of a natural. To do that you get much more heat in the cylinders and valves. I have been doing my own overhauls for about 50 years and get to see the heat damage. If you're in a hurry, you get a short overhaul cycle. Period.
On the other hand, I easily get 6-8000 hours on the same turbo engines. I run at 1500 and don't run fast to " clean it out". I also keep the oil clean. I change turbo bearings at 2000 hours and have never lost a turbo. Naturals get 10,000 with care and it's not uncommon to run into naturals with twice that.
Turbo 71s have lower compression pistons, different injectors and probably cams. The easy solution is to slow down. I would find the speed with the best fuel economy and that speed should greatly extend the engine life. Probably about 1200 - 1400. Keep the intercooler clean.
I have 2 671 naturals in the 83' boat I live on. In the ocean I cruise at 10 knots at about 8.5 gallons an hour. 1800 rpm. With 2 12V71TIs I could do 20+ knots but I'm retired and in no particular hurry. I don't need to get somewhere fast just to anchor and take a nap.

That, mate, is one of the best answers we've ever had on YF. So true. I've had 5, 7 and 9 Series DDs and love'em all. Just don't try to scream the ass off them, they'll last for ever.

Thanks Lepke. That was very helpful and makes sense. Only issue is, when you buy a used boat you do not know the history of the engines.
It sounds like you have owned a 61 Hatteras MY. Have you been happy with it? Thanks.
Capt Michael

On used engines, a good DD mechanic will have a tool that goes in the injector hole. You can do a compression or leak down test and get a good idea of the condition. That's a lot more info than starting ease, speed, what color smoke or any smoke at all. Oil is one of the keys to long life. The sleeves have cross hatched scratches put there from final honing. Those scratches carry oil to the upper sleeve and top rings. Dirty oil and excessive running at no load will smooth out the surface, cutting off the oil.
On my boat, a 1942 Wheeler, I have a centrifuge and my engines are plumbed for draining and pumping the oil to a holding tank. Whenever I have time after running, I centrifuge the oil and return it to the engines. The oil comes back transparent. Prior to a centrifuge I used a bypass filter. If you don't have dirt in the oil, it's difficult to wear the engine.
Detroits are my favorite engines within the power ranges available. If I can get the power needed with a natural, even with more cylinders, that's my 1st choice. Not that turbo models aren't good engines. Detroits are the most reliable diesel I know of.
I never had a Hatteras, but they're a great ride. I had one along side at anchor several times. My experience is mostly commercial marine. I come from a maritime family. My father was a chief engineer and uncles were captains, etc. I did ships, commercial fishing and tugs. When young ran a tug with a quad - 4 - 671s on a single shaft. Popular before the 12v. I also ran twin 6v53s in a PBR, 12v and 671s in the navy.
My '42 Wheeler looks similar to a Hatteras except for the 1/2 cabin top on the foc'sle. My deck on the bow is clear and I have a 7' headroom on the deck below. It was built as a CG patrol boat. It served at D-Day, later in the Pacific, was sold to a fisherman, raised a family on board, and professionally converted to a yacht to a Monk design in the 1970s. From then until I bought it, the boat was used as a charter for PNW inland passage tours and trips to Mexico and points south. I don't think the last owner did too well. The boat was run down, no real maintenance for years, mains and generators needed overhaul, hadn't run in 6 years, etc., when I bought it. I wanted a good sea boat, big enough to haul friends, but small enough I could run it solo, and something to keep my body going in old age.

You can take the air box covers off on one side and blower off on other side and look into the liners no special tools required on DD's

Lepke,
Thanks for your input - you obviously have a great deal of experience with DDs. One nice thing about DD is that they can be rebuilt.
Capt Michael

I'm, very interested how you centrifuge the oil?
Do you have some pictures?

Centrifuge I use is similar to picture. Info here: https://usfiltermaxx.com/en/
I think these were originally made for cleaning waste food grade oil for utilizing in auto diesel engines. I have a friend that runs hundreds of gallons a year thru his Ford Powerstroke.
The way my system works, oil is pumped to a holding tank after running. The holding tank lets air caused from pumping escape. The oil is heated to 180°F and fed by gravity to a valve that controls flow to the centrifuge. As the bowl spins, the oil rises to the top and is channeled back to the engines. The dirt deposits on the inside bowl sides. The bowl holds the water and sludge until turned off. It then drains into 5 gallon bucket that goes to the waste oil tank at the fuel supplier. I also run the oil from my Ford diesel. 2 years on the current oil.
The oil flows at about 1/8 to 1/2 gallon a minute depending on how dirty it is. Fuel can be cleaned at about 50+ gallons an hour. You set the flow by how clean you want the oil or fuel. Fuel cleans really easy. Even nasty stuff. It takes me about 20 minutes to run the oil for 2 mains and 2 14kw generators. I change the oil filters once a year. I open them, but they're always clean. They do catch some water. I use Delo 400 because I use it in my truck. The bigger diesels don't seem to care. Because my oil is clean, to dispose, I mix with diesel and burn in my hydronic boiler.
My routine is, after running I open the drain valves in any engine with hot oil, turn on the pump, when it sucks air I shut it off and close the valves. Turn on an electric element (from a water heater) and let it sit about a half hour. Overnight if I'm lazy. The tank is insulated and has a thermostat. I have planned, but haven't yet plumbed a return system. Now I use a couple 2 quart pitchers and monitor the oil and transfer it back to the engines. Then add any needed new oil. I do oil tests and originally kept the oil separate for each engine. After a few tests I let it all run together and just sample the oil existing in the engines at that time. The first test after the centrifuge, the testers called to ask why I was testing almost new oil.
If you're interested, the site above has better info and pictures of the dirt scraped from inside the bowl. Not as good as the Delaval centrifuges we had on ships, but thousands cheaper.
Capt J: I don't want to start a argument. I first went to school on radial aircraft engines. They taught a lot of engine theory. I was a kid and thought I was going to race. You know kids... Later several manufacturers diesel schools. Family connections. FM, Cat, Detroit and Cummings. Free to me. I only repeated what I was taught about cross hatching at them all. I never really worked as a mechanic. I did freelance, my own and owned a couple marine businesses. I've seen a few hundred used sleeves. The x-hatching lasts in a cared for natural 671 about 7000 hours. About 5000 in low temp TIs. Long past breakin. If you're somewhere there's no parts, you can re-x-hatch and go several thousand more hours on the parts you have.

As far as I am aware the cross hatching allows a film of oil to remain to provide lubrication to the ringpack.

I am familiar with these Glacier centrifuges. They work well.

https://albion.com.gr/2015/12/17/glacier/

That's pretty good reading. Would enjoy seeing a photo.

In Canada and a sister ship in Normandy

Centrifuges: The small centrifuges depend on oil pressure to spin. They don't separate dirt as well. The good bypass filters work about as well as the small spinners. If I run mine slow enough I get nice gold colored clear oil. Normally I run a flow rate to give me transparent but not clear. Particle size is well below 1 micron. I've been playing with the clean oil concept since I saw a toilet paper bypass filter in the 1960s.