Reply
 
Thread Tools Search this Thread Display Modes
 
Old 04-30-2019, 12:22 PM   #1
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Overhauling a J&T Detroit 671N

If there is interest from anyone to follow along, I thought I'd post a thread on the overhaul process of a Johnson & Towers Detroit 671 from 1977.

This really isn't a recommended kind of thing to do. If the boat was worth more, a repower would be appropriate. But my boat is a 42' 1977 Uniflite Double Cabin commonly referred to as a 'blister boat' due to a fire retardant additive used at that time. It has small bumps in various areas that would cost a lot to have repaired and then they come back over time anyways. It will never be worth much financially, but I am happy to use the boat as long as it suits my purposes. However, one engine was neglected by a former owner (along with other items) and it needs to be rebuilt, so I'm doing that.

The boat is on the hard for this process along with a full bottom job, thru hulls service and a few other items.
__________________
Advertisement

sbman is offline   Reply With Quote
Old 04-30-2019, 12:41 PM   #2
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
The first step was to aquire some spare parts.

Detroits can be identified by the model number stamped on the block. This is an 8 digit number separated by a dash. Mine is 1062-7000

1062-7000 = Series Inline 71
1062-7000 = The next two digits are the number of cylinders, 6
1062-7000 = This digit is the 'Application designation'. 2 = Marine
1062-7000 = Engine arrangement. A code that determines rotation and accessory drive positions. 7 = Counter Clockwise rotation (viewed from rear of engine), blower on stbd, exhaust on port
1062-7000 = Head type. 0 = 4 valve, "N" type
1062-7000 = Model variation. Unclear exactly what this denotes.

This guide is very helpful in identifying a detroit diesel: http://engine.od.ua/ufiles/DETROIT-M...ial-number.pdf

The engine as it came out of the boat had suffered some corrosion in the blower and one or more cylinders, as well as having had water run in the cooling system which caused rust problems in the heat exchanger.

Needing parts like a blower, I found an industrial generator that was in 'running' condition and had a Detroit 671 with a model code of 1063-7000, which is almost the same motor. The blower, head, camshaft, etc... all the same. Rebuildable spares for the blower, oil cooler, etc...

The engine also came with a steel skid as well as a 75KW generator head.



2,000 pounds of generator headed for the scrap yard.
__________________

sbman is offline   Reply With Quote
Old 04-30-2019, 12:42 PM   #3
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,000
Might be a good time to media blast the hull bottom and let it dry out while you are doing the work. SD has such low humidity that in a month or two blisters might dry themselves out. Then do a barrier coat and the blister problem is gone.
Ski in NC is offline   Reply With Quote
Old 04-30-2019, 12:45 PM   #4
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Next up is to tear down the donor engine and set all it's parts aside.

Mostly torn down:



A pile of big parts:

sbman is offline   Reply With Quote
Old 04-30-2019, 12:46 PM   #5
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Quote:
Originally Posted by Ski in NC View Post
Might be a good time to media blast the hull bottom and let it dry out while you are doing the work. SD has such low humidity that in a month or two blisters might dry themselves out. Then do a barrier coat and the blister problem is gone.
That's exactly what I'm doing. Will be receiving a two part barrier coat. The blisters were all ground open and allowed to dry out. They are getting filled with fresh glass set in epoxy and then a final barrier coat before bottom paint goes on.
sbman is offline   Reply With Quote
Old 04-30-2019, 12:51 PM   #6
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
The engine has to come out of the boat. I needed a crane for that. Uniflite thoughtfully provided a huge, removable hatch in the salon ceiling to facilitate engine removal, so it was able to go straight up. The crane was large enough that lifting the engine was no issue at all.



You can see some patching and filling of the flybridge cap going on in the background as well. The radar arch had to be removed for truck transport and will be bolted back on later after re-launch. Engine loaded on to a trailer for transport to the workshop.

sbman is offline   Reply With Quote
Old 04-30-2019, 01:03 PM   #7
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,000
Might consider going through the other engine too, even if it seems ok. Nice to have both clocks set to zero!
Ski in NC is offline   Reply With Quote
Old 04-30-2019, 01:04 PM   #8
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Starting the tear down on the boat engine. Lots of surface rust to deal with.

Injectors are out, head bolts pulled and rigging up the chains for head removal.

I'm using a 2 ton chain hoist and an A-Frame to manage the lifting. The head weighs at least 200 pounds.

sbman is offline   Reply With Quote
Old 04-30-2019, 01:07 PM   #9
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Making notes of all the consumable part numbers to add to the operations manual on the boat.

Fuel filters.

sbman is offline   Reply With Quote
Old 04-30-2019, 01:16 PM   #10
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Quote:
Originally Posted by Ski in NC View Post
Might consider going through the other engine too, even if it seems ok. Nice to have both clocks set to zero!
It was run regularly and it is decent shape. However, I'm doing hoses and other services on it as well. BOth engine only had about 1200 hours on it. The neglected engine developed an injector problem and a former owner didn't fix that and just let it sit, while using the other engine.

After a few years of neglect, the motor was stuck and would not turn over. The blower is seized up with corrosion as well as a couple of rusty cylinder liners. The rest of the motor is in good shape and shows little wear so it's a good candidate for rebuild.
sbman is offline   Reply With Quote
Old 04-30-2019, 03:35 PM   #11
Guru
 
Ken E.'s Avatar
 
City: Bellingham WA
Country: United States
Vessel Name: Hatt Trick
Vessel Model: 45' Hatteras Convertible
Join Date: Nov 2016
Posts: 751
Thanks for posting this. Please post your progress as you continue. Have you done a lot of major engine work like this before?
__________________
Ken on Hatt Trick
Ken E. is online now   Reply With Quote
Old 04-30-2019, 03:40 PM   #12
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Quote:
Originally Posted by Ken E. View Post
Thanks for posting this. Please post your progress as you continue. Have you done a lot of major engine work like this before?
This will be aprox. my 10th full size engine rebuild. Over the years, I've rebuilt multiple Toyota engines (including their big 1FZ-FE inline 6), a couple of ford 390 V8, a couple of honda engines, a Lycoming aircraft engine, a datsun, and a couple of others that slip my mind...

This is the first diesel though and the heaviest of them yet, the first one I need a hoist for individual parts.

I'll keep posting up as I make progress.
sbman is offline   Reply With Quote
Old 04-30-2019, 05:58 PM   #13
Guru
 
Airstream345's Avatar
 
City: Seattle, WA USA
Country: United States
Vessel Name: FORTITUDE
Vessel Model: Bluewater 40 Pilothouse
Join Date: Jul 2017
Posts: 517
Great post and yes please keep updating TF on your progress.
__________________
FORTITUDE
Blog: mvfortitude.com
Instagram: @mvfortitude
Facebook: Bluewater 40 Owners Group
Airstream345 is offline   Reply With Quote
Old 04-30-2019, 07:01 PM   #14
Guru
 
Sailor of Fortune's Avatar
 
City: Saint Augustine, Fl.
Country: Port of St Augustine ,FL
Join Date: Sep 2009
Posts: 2,437
The 6-71 will probably be the easiest of your rebuilds. Other than the weight issue of parts and block.
__________________
Jack (Steve?)
Sailor of Fortune is offline   Reply With Quote
Old 04-30-2019, 09:00 PM   #15
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,000
Make sure you properly fit the dry liners. They come in grades to get a slightly snug fit. Either need to test fit liners or scope block bores with an accurate bore gauge. Been a long time since I did it, but details are in the manual. Old liners should be marked on the OD, but that does not guarantee a good fit.
Ski in NC is offline   Reply With Quote
Old 05-01-2019, 03:08 AM   #16
Guru
 
City: Doha
Country: Qatar
Join Date: Jun 2012
Posts: 1,120
Quote:
Originally Posted by sbman View Post
Starting the tear down on the boat engine. Lots of surface rust to deal with... I'm using a 2 ton chain hoist and an A-Frame to manage the lifting. The head weighs at least 200 pounds.
Yep it took two of us pulling my old 6-71 head off, working in an engine space with bend-over headroom. Backbreaker. Glad you are in an open shop with a chain hoist.

Regarding to the rust, can you take the block down to its skivvies and send it out to be peened and cleaned?
makobuilders is offline   Reply With Quote
Old 05-01-2019, 07:14 AM   #17
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 18,928
"The engine has to come out of the boat. I needed a crane for that. Uniflite thoughtfully provided a huge, removable hatch in the salon ceiling to facilitate engine removal, so it was able to go straight up. The crane was large enough that lifting the engine was no issue at all."


IF only white boat assemblers would copy this concept , common on many working boats, the cost of maintaining an older boat would go way down!!!!
FF is offline   Reply With Quote
Old 05-01-2019, 08:24 AM   #18
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 7,762
Quote:
Originally Posted by Ski in NC View Post
Might consider going through the other engine too, even if it seems ok. Nice to have both clocks set to zero!


There is a current thread on boat diesel regarding rebuilding hours on 6-71 485 HP engines.
sunchaser is offline   Reply With Quote
Old 05-01-2019, 10:17 AM   #19
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Quote:
Originally Posted by Ski in NC View Post
Make sure you properly fit the dry liners. They come in grades to get a slightly snug fit. Either need to test fit liners or scope block bores with an accurate bore gauge. Been a long time since I did it, but details are in the manual. Old liners should be marked on the OD, but that does not guarantee a good fit.
I did obtain a factory overhaul manual, all 400+ pages of it, and I'll be following it carefully throughout the process. The liners that came out of it are marked as 5113953, which I believe is STD #1 and all rod bearings are marked standard and look like new. The crank looks to be in great condition as well.

Quote:
Originally Posted by makobuilders View Post
Yep it took two of us pulling my old 6-71 head off, working in an engine space with bend-over headroom. Backbreaker. Glad you are in an open shop with a chain hoist.

Regarding to the rust, can you take the block down to its skivvies and send it out to be peened and cleaned?
It would not be fun to do this in the boat's 'engine room'. ughh. I would want to rig up a chain hoist in the boat if I was going to do major service that way.

Unfortunately, there are no shops around anymore that have tank or shot facilities to clean a block this big. I've checked around. I'm sure they are available in other areas, but California has chased heavy industry away with fees and regulations to the point that it just doesn't exist anymore. What used to be a 10 minute dip in a vat of acid is now multiple billable hours of grunt work with a pressure washer, gloves, brushes and a tyvek suit. I'll be doing the clean up myself with similar methods.
sbman is offline   Reply With Quote
Old 05-01-2019, 10:29 AM   #20
Veteran Member
 
City: San Diego, CA
Country: USA
Vessel Model: 42' Uniflite Double Cabin
Join Date: Jul 2017
Posts: 72
Rusty liners

With the head off, we can see what was already known from inspecting the cylinders through the intake ports, but much more clearly.



The #5 cylinder liner is plenty rusty and #6 doesn't look great either. Unfortunately, #5 was open to the intake/blower and a pleasant sea breeze for a few years did not do it any good.

To make pulling the cylinder assemblies easy, I made a pin just the right length out of some stainless steel rod.



I slip the pin into the intake ports and then rotate the crankshaft to bring the piston up and it pushes against the pin which pushes the liner and it slides right out by rotating the crankshaft.



Once the TDC for the cylinder is reached, I pin the intake hole at the block deck, rotate the crank a bit more to pull it down into the liner about 1/2". Then I have room to put a chain onto the pin and hook it up to the chain hoist. remove the connecting rod bolts and the entire liner/piston/rod assembly comes out in one piece. It can be slid out by hand, but it's pretty heavy and awkward.



The head is off to the machine shop for a valve job, and the blower is there also for new bearings, seals and timing setup.
__________________

sbman is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 08:20 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012