671 tib's - The Hull Truth

jersey42 · 01-06-2005, 07:25 PM

looking for info on detroit 671 tib's i hear mixed emotions on them some say you have to major them after 1000 hrs and then i heard guys have 2500 hrs on them i just bought a 42' jersey sportfish with the tib's. they were just majored and only have 150 hrs on them. i have all the receipts from the owner. the owner was real maticulous with the boat. shes in excellant condition.

Fubar512 · 01-06-2005, 07:49 PM

Generally, the 71 series Detroit Disels can go upwards of 10,000 hours between major overhauls as long as the power output is kept below .90 HP per cubic inch.

The problem areas with the 71 series are its injectors (earlier, non-electronically controlled models), excessive oil consumption (due to leakage on models without air-seps) and on earlier versions, cracks in the cylinder heads between the valve seats. The last issue plagued the older, 4-valve heads back in the 1970's and early 1980s.

Now, I assume that the engines in you're boat are "B-DECs" (hence the 'B" in 6-71TIB)? If so, you've eliminated the injector issue.

I'd suggest that you go and join boatdiesel.com.

yachtjim · 01-06-2005, 09:21 PM

671 Naturals will last for 5000 hours or more recreationally.* 671 TI's will last for 2500, and 671 TIB's will last for 1500.* I know there are exceptions out there and I'm sure a few of them will correct me here, but having*been researching 100's of boats with 671's for clients over the past 10 years this is my conclusion as well as the conclusion of just about anybody I have talked to about them.

Do a search on boattraderonline and tell me how many boats with 671TIB's you can find with more than 1700 hours since new.* I doubt many as most go boom at 1500.

jbonnet · 01-06-2005, 09:41 PM

I had a 1989 41' viking with 671 TIB's and I never had any major problems with them. Sold the boat with 1800 original hours
You must change the oil at 50 hour intervals. This keeps them well lubed. They tend to leak at the blower shaft seal.
I would install block heaters with thermostates if it doesn't already have them. I had the ones that shut off at 100 degrees. Use them in the summer as well it keeps the engine room moisture down. They are not hard to install if you have basic mechanical talent. You will need to remove the fuel pump so make sure you get a new gasket for it. I got mine from Atlantic detroit in NJ. don't bother going thru J&T for them. They sent me the wrong ones twice.
You will get alot of mixed reviews on these engines but from experience I can tell you that if you take care of them they will last along time. If you have any questions about them feel free to Email me. I have a good amount of experience with them.
Good luck The Jersey is a Great boat

CB Haws · 01-06-2005, 10:25 PM

If they are 485HP they don't last long. Period!! That is just way too much HP out of too few cubic inches. My DD mechanic calls they hand grenades.

jersey42 · 01-09-2005, 11:57 AM

thanks for the info. i have block heaters but they are set up in a timer switch. did you have the 485 h.p.671-tib's.

jersey42 · 01-09-2005, 12:02 PM

also every time i go out i ramp the rpm' up slow and i bring them down slow befor returnig to the dock i don't berry the throtles and i cruise them at 2150 w/ the three blade props. i am going to put the 4 blade props on in the spring. i also let them idle in the slip for about 5 min. befor shutting them down.

Fubar512 · 01-09-2005, 12:47 PM

Idling the engines for five minutes after the boat's secured is always a good idea, especially so on turbocharged engines. This is mainly to prevent what's known as "coking", where oil thats trapped in and around the turbocharger's shaft bearings gets superheated and turns into a coke-tar like substance that can impede oil flow on the next start.

The bulk of my experience with 71 series engines has been on OTR applications (buses). I did help maintain a pair of 6-71's on a 65' party boat. and those mills went well over 10,000 hours before they required a major overhaul.

The early 6-71 TI's (360 HP, 385 HP) would wear out a turbo or two before they required a major overhaul. I'm talking almost 10,000 hours.

jbonnet · 01-09-2005, 01:19 PM

Jersey42
I did have the 485 hp. It would be a good idea to hook up thermostates to the block heaters this will keep them at 100 degrees or so all the time and it makes them start up on the first crank. You will hear a few nightmare stories about the 485 hp 671's but I would say for the most part they are great engines. I think alot of the stories are hear say. I would guess that they have probably been the most widely used diesel engine for marine applications. My friend has a set of brand new 1300 HP Man's and although they run like a bat out of hell they leak oil and he has spent plenty of cash getting the leaks fixed.
Just take care of them and they will be very relaible for you.
Good Luck
Jeff