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Old 12-20-2015, 02:13 PM   #1
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New skipper, advice please on a 1989 Marine Trader, Det D's/J&T 6-71TA's....

Hey all, looking to purchase a 62' boat here, kept in boat house all it's life and roughly 4500 engine hours, well serviced by a full time USCG licensed skipper and want to get some advice/suggestions/experience with this make and this engine. It's a Marine Trader Med Yachts make, and I am a cruiser kind of skipper, 10 knots is fine. I am not looking to do major blue water, mostly Puget sound and inner passage stuff. I am also seeking to live on board when retiring.
Boat also has fuel polishing, twin North lights gen sets, low hours and appears in great shape.
My question to the audience, anyone with a Marine Trader of 1988-1991 era, how are they holding up? DD's by J&T thoughts? Parts appear easy to get and cheap. I hope to hear the good/bad and things to look for. Will go to survey in 2-3 weeks and feel the boat is fairly priced. Owners have operated with an open checkbook, according to the captain who is not the owner.
Thanks folks and any/all input is appreciated. Anyone else up near Everett, WA where I will be docked?
James
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Old 12-20-2015, 05:15 PM   #2
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Good luck with this. Not familiar with this boat in particular, but have been doing a LOT of reading as I am too in the hunt.

The "genre" of id to late 20th century Asian built boats shares a few points to look for, although these points can apply to boats made anywhere. Make sure your surveyors (yes two, more on that later) know what he's doing.

* Water intrusion into the laminate with resulting de-lamination, ESPECIALLY when there are teak decks installed with their associated 3000 screws.

* Steel tanks, if installed. The leaks mentioned above get water on top of the tanks, which then rust out. Their removal is often a huge job. Replacements are also pricey.

* Electrical wiring. Non-tinned wire, corrosion.

* Leaking windows, see the first point.

*The DD 6-71, with proper care, feeding and regular but not over strenuous exercise will last a looooong time (10,000 hours is not unheard of). It is a sleeved engine, and can be rebuilt in situ. Unless something really catastrophic happens the block itself will last forever. Get a GOOD DD mechanic to do the engine survey. Insist on oil and coolant analysis. If you can get the parties to agree do a compression check. More money, but peace of mind.

INSIST that the engines are not run for at least 48 hours before the engine survey. The mechanic HAS to hear a true cold start. Check the temps (invest in an IR temp gun) when you arrive on the scene. If they have some BS story about "had to move the boat" or something, cancel the engine survey.

Insist on a sea trial.

These are the biggies.

Good luck.
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Old 12-20-2015, 07:00 PM   #3
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4500 hours on a J&T DD is a BUNCH. 6-71 NAs will run 10,000 hours but not the jacked up J$Ts. Factor in an inframe rebuild with your offer. If its been undercover its whole life you wont see the evidence of leaks so much,,, it has them. What gears does it have ? Gear ratio ? Shaft size ? Lots of things to look at !!!
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Old 12-20-2015, 07:16 PM   #4
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As a newbie, I don't totally understand what the J&T upgrades do or what an "inframe Rebuild" consists of? So anything you can elaborate on this would be most helpful. From what I read, the Detroits are simple/good engines at low RPM's, correct?
Thanks again.
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Old 12-20-2015, 07:40 PM   #5
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Not sure where the "jacked up" part comes from in a J&T. AFAIK they rebuild to factory specs. Am I missing something?

Yes, DD's are simple low RPM engines. If you maintain them and run them at low RPM.

The term "inframe rebuild" is more applicable to the trucking world, but the principle is the same. Pull the heads, replace. Pull the oil pan, remove the rod caps pull all the pistons, rods. Pull the sleeves. Replace sleeves, rings, bearings.

Over simplified, but about it.
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Old 12-20-2015, 07:47 PM   #6
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Quote:
Det D's/J&T 6-71TA's....
I think (I don't really know) that the turbo and aftercooling was where the "jacked up" came from. If these 6-71's are putting out over 400HP each then I think 4500 hrs is a lot. Again...I don't "know".
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Old 12-20-2015, 07:50 PM   #7
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DDs are anything but simple. They are much more complicated in design than a 4 stroke diesel. Much more moving parts and more application specific designs than most other makes. The 6-71 can be had from 165 hp up to 485 hp, all on the same standard block, mostly. J$T was famous for squeezing a BUNCH of hp from just about any DD. A J$T 6-71 at 485 hp generally will only last 3000 hours, if well cared for. Of course, how it was operated is a factor. That same engine ran at low power is usually a stinking, smoking pig that needs to be spun up every so often. However, at 210 hp with N50 injectors and no turbo it will happily run at 1250 rpm for years on end. Different compression ratio, cam timing, port height, etc. There are so many configurations for these engines that it boggles the mind. And, its getting really hard to find old school DD mechanics that actually know them. An "inframe rebuild" is simply new pistons, rings, liners and rod bearings. Have the heads checked and turbos looked at. You WILL find lots of exhaust problems, so plan on all new risers and blankets if dry turbos. Wet turbos and there corresponding manifolds have there own problems. You REALLY need to know exactly what engines it has.
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Old 12-20-2015, 07:55 PM   #8
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Ah, missed the turbo part. Yes, cranking that many horses out will come at a price.
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Old 12-20-2015, 08:27 PM   #9
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We moor in Everett and it has a lot of rain. So if the boat been under cover, I would require the boat be moored out in open cold and rain for a period of time. Unless you are planning to moor it under cover.

The DD 671 is a one of the longest lasting long proven history and parts service is readily available. However the J&T add turbo and over sized injectors which increases the horse power and RPM which tends to shorten the live. What shorten kills most engines is not the engine but what hangs off them and increasing the HP & RPM. So check the maintenance and it's present condition. One quick way is make sure they start the engines COLD, and listen how hard they start and watch what comes out of the exhaust. Phil, Everett Marine Service is my mechanic, who I recommend. A 671 can be rebuilt in place, rather than having to replace and/or taking it out of the boat. Which when it comes time to rebuild is cheaper and easier.

Anyway make sure you use a surveyor not recommended by the broker owner.
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Old 12-20-2015, 08:57 PM   #10
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Kulas44, thanks so much for all the tremendous insight to this newbie. The engines are 485 hp, 6V71TA's with 4500 hours and run almost exclusively at 1650 rpms and 11 knots. Max speed according the the USCG captain is 15 knots. They have been well cared for. Here is the quotes from the captain.
11 KTS -------- 1650 rpm
15 KTS --------- Dont remeber we always run at 11 kts. The boat just seems alot happier there

Oil Burn
It depends mostly on the tide and the sea condition. Average would be about 1 - 2 qts every 100 hours. WE have had weeks of running with no oil burn.

Last what I would call major maint. would be last year we pulled the port blower and had it rebuilt. It was working fine except for the seals were leaking.

All injectors and lines were replaced about 2 years ago.
Any and all comments are welcome here.
Thanks everyone....
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Old 12-20-2015, 09:01 PM   #11
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Phil, thanks so much..will be mooring up next to you this spring if all goes through. The north part of Everett has some slips open...was up there for 20 years before moving to CA and selling my boat, but miss the NW boating, crabbing, San Juans, etc.
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Old 12-20-2015, 09:11 PM   #12
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Phil, any guess on what a rebuild would run for the engine I am talking about? I see a bunch of rebuild kits Ebay and other places for a reasonable amount.
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Old 12-20-2015, 09:17 PM   #13
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You need to find a Detroit 2 stroke specialist to give those engines a very thorough survey. What some guy may say, and reality over those 4500 hours could well be very different things. Just about any moron with some sea time can get a USCG ticket so don't give any credence to that. Caveat Emptor!

To rebuild a turbo Detroit correctly by the right person, figure 3,000 a cylinder. You'll have a literally new engine, but the mechanic is the whole game. Then you have the transmissions.....
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Old 12-20-2015, 09:20 PM   #14
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Quote:
Originally Posted by Capn James Brett View Post
Phil, thanks so much..will be mooring up next to you this spring if all goes through. The north part of Everett has some slips open...was up there for 20 years before moving to CA and selling my boat, but miss the NW boating, crabbing, San Juans, etc.
Where is the boat presently moored. The north marina is all open so make sure its PNW rain winter ready. We are moored on the commercial dock south marina. Everett has a 75 ton lift and a well service parts and yard. The water is brackish which is easier on the boat than the salt.
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Old 12-20-2015, 09:34 PM   #15
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Originally Posted by Capn James Brett View Post
Phil, any guess on what a rebuild would run for the engine I am talking about? I see a bunch of rebuild kits Ebay and other places for a reasonable amount.

As mentioned its the mechanic not the parts that is important. Parts are readily available.
I don't know what it would cost.
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Old 12-20-2015, 09:35 PM   #16
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Originally Posted by Phil Fill View Post
Where is the boat presently moored. The north marina is all open so make sure its PNW rain winter ready. We are moored on the commercial dock south marina. Everett has a 75 ton lift and a well service parts and yard. The water is brackish which is easier on the boat than the salt.
Phi, presently down in Texas and has been under a boat house cover all it's life. Teak decks and that is what scares me about Everett....rain, rain, rain. Will look forward to meeting you this spring. Thanks again.
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Old 12-20-2015, 09:41 PM   #17
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I would "think" that a pair of 210 hp NA DDs would be a very much better engine for the way the boat has been operated. The 485s have a lot of extra and expensive equipment that is not being utilized. Turbos, big raw water pumps, big (sloppy) injectors, etc. If it were me ,as I said previously, I would subtract from the asking price for the rebuilds then have them done to 210 hp specs. Simple enough, just different pistons and liners. Same price. Leave off the turbos and reconfigure the exhaust. Resetting the cam timing would be an additional expense but neccessary. You would need to remove the bellhousing adapter to access the gear train. It probably has Allison gears, which are really good and easy/cheap (relatively) to work on. TwinDisk are also good and J$T used them a lot. Not so cheap/easy as Allisons. At any rate the gears would need to be removed to replace the rear crankshaft seal. I would NOT buy a boat with 485hp 6-71s with 4500 hours on them unless it was priced appropriately. A complete inframe usually runs about $3000 per hole, so $18000 per engine is $36000. Much cheaper than a total repower at about $60,000. Any good DD mech. will tell you that those 485s dont have much (if any) life left. Do a lot of research before pulling this trigger.
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Old 12-20-2015, 10:19 PM   #18
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I run J&T 6-71TI s in my Viking 450hp.
Listen to Kulas he's correct. I also am extremely skeptical about the reported oil consumption reports you were given. Try about 1qt for every 10 hrs at 1900rpm.
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Old 12-20-2015, 10:24 PM   #19
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Quote:
Oil Burn
It depends mostly on the tide and the sea condition. Average would be about 1 - 2 qts every 100 hours. WE have had weeks of running with no oil burn.
Scratching my head on this statement.....

Quote:
DDs are anything but simple. They are much more complicated in design than a 4 stroke diesel.
Heck no. They are the large diesel equivalent of a lawn mower engine. What makes them so more complicated?
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Old 12-20-2015, 10:28 PM   #20
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Phil, any guess on what a rebuild would run for the engine I am talking about? I see a bunch of rebuild kits Ebay and other places for a reasonable amount.

Just had a DD J&T in frame rebuild by Detroit Diesel. Cost was $15k and took one week. Labor was about $8-9 of the total. Great motors, don't run them hot and they will last a very long time. Just remember - if they aren't leaking oil something's wrong!
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