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671 T smoking badly-grey blue smoke

  • Thread starter Thread starter Genevatexan
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Genevatexan

Genevatexan

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Guys,
My '76 starboard 671 Turbo (4 Valve) is getting worse. We had a raw water impeller fail two weeks ago (185-190 degrees before shutdown) and misdiagnosed as a thermostat. Replaced that, retested and with new IR thermometer quickly found raw water impeller housing overheated. Engine got to 192 degrees by the time shut down at slip. R & R- new impeller, fish blades from intake and output to intercooler, pulled down intercooler inlet, clean everything, now everything fine. But now at more than 1000 rpm I am blowing blue smoke big time and some blue/grey smoke at idle.
We have tried fuel additives, checking Turbos, unistalling cleaning and testing intercooler for water and air, checking emergency flap on blower intake, nothing. It looks to me like oil blowby on the rings. (2400 hours). I can get a diesel guy to my site to run the rack and run compressions, but based on where I am, its over $1K just to do those two things.
Engine runs 23-25 lbs of oil pressure at idle and starts and runs fine. its just turned into mosquito fogger and its not black smoke, which I would assume is fuel. Its blue grey. I will change both fuel filters this weekend, but that is the end of the list I have to check so far.
What is my next diagnostic step before I drop the $1,000. Is rings and liners an in-the-boat job and how much of disasembly/prep can I do before I am dangerous...?
 
Bet a boatbuck it's busted rings or a distorted liner from the overheat (it does not take long)

Compression check will only ID which hole(s) went bad. Assuming you are SURE it's not a bad turbo or blower, I would save the $1k and replace the rings & liners. If you are not sure, the $1k might be money well spent. Please don't go cheap and fix only the problem holes.
 
should be able to in frame that ok....assume those are V series...last quote I got from florida DDA in Tampa 3 yrs ago was 35k to do both engines. That was in a '84 42 Bert same as yours...I did not buy, even though the owner dropped 40 k off the price...engines were shot at 1200 hrs due to undersized HP for that boat, owner had it wot 2600 and then would run many days at only 1200.
 
Depending on your comfort level, you could pull the air box inspection plates and look at the pistons, rings and cylinders. You may have to have bar the engine over to get a complete look. A cylinder problem causing that much smoke may well be visible.
Will
 
I have big bar and socket to fit crankshaft bolt on the front so bar over is possible. This is a straight six and inspection plates are on the gunnel side if I recall. Any trick to removal and replacement? Will probably try that this weekend. Also, if liners and pistons on all 6 holes in boat is solution, what should I expect for cost if done by qualified mechanic? (assume this is less than a full rebuild because not looking at bearings, and other hard parts...)
Finally, how much of tear down and make ready is within the reach of an average mechanic (me)? I own sockets, ratchets, breaker bars, torque wrench, and have an average auto-mechanics skills for diagnose and repair (starters, carbs, suspension, electronics,etc.).
 
You could tear down quite a bit, drain the oil for sure as the pan has to come off, be sure to clean the bearing surface of the oil pan and engine surface really well, you may need the special socket to remove the fuel tubes at the injectors or injector if doing only one..the cylinder head id "heavy" really heavy...do not drop on toe !!!

I would suggest only DD certified Mechanic do re assy, and set up. not some guy who says he is..

Keep everything really clean.
 
I am doing a rebuild on one of my 671TI's currently. The hardest thing I had to do thus far was to remove that head.
I wish someone would have warned me ahead of time that even though you drained all of the oil out, when you lift the head it seems as if a few more quarts come out all over your pants and shoes.
 
I would suggest 2 pairs of strong hands to re install.
 
Canuck Dennis said:
I would suggest 2 pairs of strong hands to re install.
Click to expand...
Like a dummy, I took the head off before I built the frame to lift the engine.
When I go to reinstall, I will lower it down with the two chainfalls that I now have on the frame.
It should be much easier.
 
Genevatexan said:
I have big bar and socket to fit crankshaft bolt on the front so bar over is possible. This is a straight six and inspection plates are on the gunnel side if I recall. Any trick to removal and replacement? Will probably try that this weekend. Also, if liners and pistons on all 6 holes in boat is solution, what should I expect for cost if done by qualified mechanic? (assume this is less than a full rebuild because not looking at bearings, and other hard parts...)
Finally, how much of tear down and make ready is within the reach of an average mechanic (me)? I own sockets, ratchets, breaker bars, torque wrench, and have an average auto-mechanics skills for diagnose and repair (starters, carbs, suspension, electronics,etc.).
Click to expand...
It would be a sin to get that deep into it and not change the bearings. You have to tear down the engine to do the kits anyway. You have more than enough hours to warrant a full rebuild. If you have to tear it down, do the whole thing. It will be much cheaper in the long run.
 
Genevatexan said:
Guys,
My '76 starboard 671 Turbo (4 Valve) is getting worse. We had a raw water impeller fail two weeks ago (185-190 degrees before shutdown) and misdiagnosed as a thermostat. Replaced that, retested and with new IR thermometer quickly found raw water impeller housing overheated. Engine got to 192 degrees by the time shut down at slip. R & R- new impeller, fish blades from intake and output to intercooler, pulled down intercooler inlet, clean everything, now everything fine. But now at more than 1000 rpm I am blowing blue smoke big time and some blue/grey smoke at idle.
We have tried fuel additives, checking Turbos, unistalling cleaning and testing intercooler for water and air, checking emergency flap on blower intake, nothing. It looks to me like oil blowby on the rings. (2400 hours). I can get a diesel guy to my site to run the rack and run compressions, but based on where I am, its over $1K just to do those two things.
Engine runs 23-25 lbs of oil pressure at idle and starts and runs fine. its just turned into mosquito fogger and its not black smoke, which I would assume is fuel. Its blue grey. I will change both fuel filters this weekend, but that is the end of the list I have to check so far.
What is my next diagnostic step before I drop the $1,000. Is rings and liners an in-the-boat job and how much of disasembly/prep can I do before I am dangerous...?
Click to expand...

Doing the compression test is actually pretty easy once you have the valve cover off.
You can purchase the gauge and adaptor for less than $150.00 off of the net.
Pull the air box covers and see what the cylinders look like with a borescope. You can also check the ring tension at that time with a small screwdriver. Stuck top rings are common as they do not get enough oil.
Be careful when bolting the covers back on as the Detroit manual states that if overtightened, you can distort the cylinder.
 
I have heard some huge numbers on the full rebuild so I am nervous about simply not being able to pay for it, and not being a strong enough mechanic to do the detail work on my own.

If we do the bearings as well, does the engine have to come out? If the engine has to come out can the gears stay in?

On a different thread, I saw 2 guys, 1 day for rigging and removal, presuming boat is on the hard, and engines stripped and disconnected as far as possible. Something north of $1K in labor, plus boat haul out, the lift, and a jig for removal, did we say around $3K to get it out or is that optimistic?

From there if I ship it to a shop, what is a fair number to rebuild the whole thing? If its $40K, its over half of what I paid for the boat, and the boat is only worth about $55K today and falling... the math is bad.....
 
If youve ever done rings and bearings in an automotive unit, you can do this. A shop manual (Real Detroit, not a Clymers) will give it to you bolt by bolt. Plan on about 10 hours sitting on the crapper reading before you tear into it. Read it over and over.
Youll need a 3/4 drive set for the big stuff like headbolts and mains, lotsa coffee cans, and wall to wall plastic visquine. At least on a six banger you can sit on a bucket and plan your strategy. With the twelves theres no way!
Confer with a DD mechanic and if you feel inadequate, have him do the re-assembly. Take lotsa notes AND pictures of course! ws

kdwryu.jpg

Bottom of a 12-71 pan should be almost the same as a 6-71

2mzfxg.jpg

I had fun doing the big-boys

23hqhao.jpg

Page 347... cylinder head dis-assembly
 
Genevatexan said:
I have heard some huge numbers on the full rebuild so I am nervous about simply not being able to pay for it, and not being a strong enough mechanic to do the detail work on my own.

If we do the bearings as well, does the engine have to come out? If the engine has to come out can the gears stay in?

On a different thread, I saw 2 guys, 1 day for rigging and removal, presuming boat is on the hard, and engines stripped and disconnected as far as possible. Something north of $1K in labor, plus boat haul out, the lift, and a jig for removal, did we say around $3K to get it out or is that optimistic?

From there if I ship it to a shop, what is a fair number to rebuild the whole thing? If its $40K, its over half of what I paid for the boat, and the boat is only worth about $55K today and falling... the math is bad.....
Click to expand...

It shouldn't have to come out unless you have major core damage or access is extremely limited. The bearings are not the issue. The engine needs to be stripped down and the pan needs to be dropped if you have 1 bad hole or six. Find a good mechanic who you can trust. Let him evaluate the engine before you start doing anything. If it needs a rebuild, get a quote for what it will cost and what it will entail. Then you can decide if it is worth it or not. No way a 671 should cost 40K to rebuild. If that was the case you would do better to repower with modern remans. FWIW it cost me 15K to rebuild a 6V92TA. I already had all new hoses and clamps so that helped keep the price down.
 
Last edited:
What HP are these engines and what is the rated RPM....

"Find a good mechanic who you can trust. Let him evaluate the engine before you start doing anything."

yes, don't go "fixing" things without a diagnosis first...Running a DD at 190 degrees with good oil pressure does NOT lead to some catastrophic problem...

A mechanic can check the crankshaft and bearings...I don't know what the incremental cost is for redoing those, but if your engines are not the high HP high RPM variety and you are a 100 or 200 hours a year boater, those would not be high on my priority list for a smoke issue....

Bill's suggestion about doing the disassembly yourself and having a trusted mechanic do the reassembly is one good option....maybe you can be the assistant and learn tricks in reassembly....knowing what to replace based on experience is valuable.
 
Why jump to conclusions? It seems a bit premature to talk about rebuilds until you know what the real problem is. Just call DD and get them out there to see what's wrong. After that, you'll know what you've got and can discuss the options.
 
In the imortal words of uncle Willy "'em ere's diesels their gona smoke" run it till it blows.
 
We will do the bore-scope this weekend, and a little more testing. This engine has always smoked in the exhaust until it warmed up. But now the problem is 10X worse and occurs with a fully warmed engine. But I'll take it a step at a time, and pull in the right guys as we go. We got cross with Stewart Stevenson over a justifiable issue 2 years ago so the relationship there won't work. But I do have access to some other reputable diesel service guys who can get involved as needed.

Good advice all the way around, and much appreciated. I will build a photo history as we trouble shoot and solve.
-K
 
Up north, Toledo way my friend paid $1,200 per hole for his 6-71's a few years ago.

BILL
 
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