Confusion about engine specs

the 485 hp is the 671 TIB, it has a bypass. The TIB has different injectors, turbo, and a bypass blower.
You can easily tell the TIB vs the TI because the TIB has the bypass assembly under the blower and air plumbing that goes into the inboard rear inspection port.
Also the injectors and turbo are different, but you cant tell from looking at the engine.

The later era DD 6-71 came in a range of horsepower from 310NA to 385, 410, 415, 425, 450TI t0 485TIB.

The 410hp DD 6-71TI is a great motor. Far more service life than the 485hpTIB. The 410's were common in the slant version.

It is not uncommon for listings to have inaccurate specs. An inspection by a qualified DD mechanic would be your best technical source.

Give Ed Tevis a call at J&T, I believe they were supplying the engines to Post at that time. He will have all the details and can potentially give you a copy of the factory sea trials if you can provide him with the engine serial numbers: http://www.johnsontowers.com/marine/reman

The J&T 6-71 TI rated at 410hp is a good rating for this engine, much more reliable than the 450 or 485hp versions. Make sure you have the Walker Airseps to keep things a bit cleaner in the engine room. I would be concerned if the boat has Capitol Gear Boxes as they are no longer manufactured and service / parts is a challenge. Twin Disc or ZF is a better option.

Find or get the serial numbers. Should be documented in a past survey I'm sure the broker has or can get. That's the key to a world of much information. Then tap on your favorite DDC shop. They can fill you in on all details of the original order and offer a factory part listing for those exact engine.
J&T may have added some extra options but the DDC list will tell what was ordered and delivered. Probably who (whom?) they were delivered to.

I recently understood, that 6-71 TI HP ratings depends on the chosen injector size…
Correct me if I’m wrong!!

Injectors are a great part of HP changes. Piston types, fuel pump, 2/4 valve heads, tall vs original height blocks, cam timing, air cooling, blower ratios, turbo performance, exhaust tuning AND more, represent other parts of creating HP on any 2-stroke DDC block.
Any of these components can be adjusted and weighed against engine life. Some aftermarket shops and installations did well, some not so well. I think 485hp was the big wall on da 671.
410s I think had a pretty good life IMO.
I always thought the ole Post were ideally powered vs life of the motor and NOT high strung. Have an old Post next to me with pancake 671s. Last I saw her run (long ago), it was impressive. Another with 8v71Ns is my fave. Been surrounded with Post these last few weeks. I understand another 2 slips away has 8v92s. She has to fly.
But all that know me here, I'm a 71 guy.

Have your soon be yours surveyed well. Get tight with a proven good local shop and bring them coffee often. No matter what anybody says, a good old Detroit tech (NOT some bilge punk) can be a very good friend (to many punks out there).

71s rule,
rc

J&T is an excellent source.
I have been in contact with them and the had the original build sheet and sea trial results for my boat.
All you will need is the serial numbers.

Just keep in mind that the engines could have been modified over the years.
To be 100% sure you will need to have a tech pull the valve cover to see what is stamped on the injectors and get the part number for the turbo.

Mainly WHO marinized them. Each company J+T, Covington, S+S, etc. Used different injectors, turbo's, injector timing and other bolt on parts mainly that changed the HP rating. J+T was used mostly by Post as far as I know, if not exclusively and usually put the largest turbo's and injectors. Injector size is the majority of it, but some added larger turbo's.

Internally the heads (4 valve vs 2 valve) and pistons (Compression) are different

This might be worth checking out if applicable ??
http://www.capitalgear.ca/aboutus.asp

If she cas Capital Marine clutches, This may be the better site to start with.

http://capitolmarinegear.com/

Boatdiesel.com maybe another good resource for Detroit Iron and gears.

With regards to parts / service on Capitol Marine gears, a lot will depend on which model gearbox it is. On some models, clutch packs and bearings are nearing "unobtanium " status, while others have some more availability. Last time I checked, full rebuild was running near $13K apiece, and that was with some scavenged / used parts. Regardless, I would check / replace ALL gearbox hoses when buying the any used boat with Capitol gears.

I just checked out the brokerage add for the boat.

if I were in the market, I would want to go see this boat.
Its hard to judge from pictures, but this boat looks real nice.

cosmetically it seems to be well cared for from the pictures, that is usually a sign that the structure and mechanics are well cared for and maintained. wax and varnish are usually the first think to go....

The mains could use some paint, but at least they didn't do a quick spray job to try to make things look nice in the ER.

UMMMMM well, don't you think a phone call or email to the source, a Detroit Diesel dealer or THE Detroit Diesel dealer that marinized yours would give you all the information you want? Does it even matter what is in them? At 410HP they last, are reliable, and aren't too high in the HP ratings and the maintanence is the same. I'd also much rather have them then the same ERA/HP Man, volvo, or Perkins, even more then a 425hp 3208 (which didn't last....at 1800-2000 hours they needed rebuilds). 410HP 6-71's should go at least 5,000 hours between majors if not abused and more than likely closer to 10,000. I could walk into either local DD diesel dealer here with your serial number and they can tell me any part that is in YOUR motor.

See, the thing is, each company that marinized them did many different modifications to get to their HP rating, depending on what they were seeking or even what type of boat they were being put in. With the serial number, just about any DD dealer can look up exactly what's in your set. All of the 410HP J+T's had the same exact parts in them from engine to engine. Some owners even had dealers modify them to achieve different things. I ran a 58' Hatteras YF where the owner had DD of Daytona install 90 LPH injectors instead of 110LPH to save fuel and for them to run cleaner on the low end, without changing anything else.

CAT's also had some varients just like the D.D.'s. The origional 3412's were marinized by either Key Power or Gold Coast marine (I can't remember which), but they have lots of different parts on/in them that aren't Caterpillar parts, some might have even been made by the dealer. Then CAT stepped up to the plate, saw enough demand, and marinized the 3412's in house. There were other engines like that as well in the CAT lineup.