Detroit Diesel Question?

[GalaxyGirl]

Originally Posted by bobconnie

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

Yup, re-sale is most important now. Although, those Hats do seem to sell

I looked at a boat here in Boston with twin Cats. Very nice boat, but I would really have to jamn the kids in. Having trouble getting the space

[Ciabi]

We just bought a Hatteras 53MY to put into the slip next to our Aries-32 sloop, "The Chester P", so we dance on both sides of the room. Our 8V 71-T's were rebuilt in-place 750 hrs ago. They're solid work horses, even after 36 years. Our sloop's auxiliary is a Westerbeke-30
, and equally as old. I redid her 3 years ago and it is very reliable.
The fluid analysis from the engine survey told us the oil was old - service and keep your 92's clean with engine room checks and they'll take care of you. The project here in the next few weeks is to change the oil in both of the old girls like the book say to. Same with transmissions. We've chosen a MY for our live aboard for many of the same reasons already stated on this thread- and luckily we can keep sailing too. :-)
Our DD 8V71T's were rebuilt at 2260 hot by a PO. Apparently they we're run at rated RPM for years going back and forth to MX. We intend more trawler- like speed here in SF Bay.

[GrowleyMonster]

If you are not doing a lot of long range cruising where fuel economy is an issue, the 12-71 is okay. 71 series engines are EXTREMELY common in crewboats, utility boats, and other oilfield vessels, partly because they are just plain cheap to buy or replace, partly because they are very simple and easy engines to work on. There is a great deal of part interchangeability between the various engines with their various number of cylinders. So parts are a little cheaper than most other diesels. But don't let the seller BS you into believing it is a "better" engine than a Cat or EMD or whatever.

Keep in mind that no diesel likes to idle or run at low speeds for very long, especially turbocharged diesels. Diesels have a fairly narrow operating speed band where you get decent fuel econ and proper operation / minimum problems. If you want to go slow and cheap, you mustn't be overpowered.

[GalaxyGirl]

Originally Posted by GrowleyMonster

If you are not doing a lot of long range cruising where fuel economy is an issue, the 12-71 is okay. 71 series engines are EXTREMELY common in crewboats, utility boats, and other oilfield vessels, partly because they are just plain cheap to buy or replace, partly because they are very simple and easy engines to work on. There is a great deal of part interchangeability between the various engines with their various number of cylinders. So parts are a little cheaper than most other diesels. But don't let the seller BS you into believing it is a "better" engine than a Cat or EMD or whatever.

Keep in mind that no diesel likes to idle or run at low speeds for very long, especially turbocharged diesels. Diesels have a fairly narrow operating speed band where you get decent fuel econ and proper operation / minimum problems. If you want to go slow and cheap, you mustn't be overpowered.

But, if you run them up every couple hours, then you should be ok?

[GrowleyMonster]

Originally Posted by GalaxyGirl

But, if you run them up every couple hours, then you should be ok?

Hmmmmm... not sure how qualified I am to completely answer that, but certainly that would be better than running half throttle for days at a time.

I think a Detroit rep would be able to help u on that.

Do you plan on cruising a lot?

When I was running crew boats we always ran wide open except when a slow bell was required or in low vis or when maneuvering. This usually powered by 3 or more 12-71s.

[mark krebs]

These engines all get about .37lb/hp-hr. That's normalized fuel economy. Normalized means divided by something, in this case horsepower-hours, to give you a single memorable number that's useful across a range of answers. That means the number's "good" for about 1300-1800 RPM. You can figure your fuel consumption directly from how many HP you need. A fancy newer engine might get as loow as 0.33lb/hp-hr, which is significant but the BIG savings comes from slowing down. Boat power is approximately cubic with speed meaning twice the speed costs 2*2*2=8x the horsepower. So yeah, slow down a bit.

I run two 8v92TA and can get 1.4gal/mile with a 70,000 boat at 10kts. At 20kts (WOT) I don't know 'cause I never run that fast for long, but I expect 5.6gal/mile (8x fuel flow / 2x speed)

[Rumrace]

V12 71CU per piston yum. “ Slober oil” is a perfect description of a Detroit. Hull length is less important than hull type and waters the architects designed it for are more important. A Favourite 1700 is lovely but for Dutch canals. Her flat stern is going to get pounded off shore. Her prow entry is going to be a wet spray view. It’s going to get great mileage in the calm waters where a Palmerston will suck fuel same engines.
I have V8’s turbos in a Sea Ray. They were okay but I don’t like big diesels any brand. 2 stroke especially. It’s more I don’t like cast iron. The Favourites are stunning aluminum boats with cast iron motors. Seems a contradiction. Buy the one with the best fuel polishing system.