8v71ti Help

[JCG]

Some of you may remember some of my post on reworking a 46 ft Hatteras sportfisher. We'll she's in the water and we have started running her some and have found that the engines need some work.

The main problem is they will not turn up to higher rpm. Based on my research on this site WOT should be arround 2100 - 2200 rpm?, cruise would be 1800 rpm or so. Also, when attempting higher speeds both engines pour out deep black smoke and start running rough. Both engines crank easily, produce a cloud of bluish smoke when cranked cold for a second or two which rapidly clears up to just a hint of blue smoke for several minutes then dissipates to no smoke when engines reach about 150 degrees. Engines idle well @ 650 rpm, start instantly when warm, and run great as throttles are advanced. The problem with black smoke begin when the rpm gets to about 1500 rpm. From this point on additional throttle results in more black smoke and maybe another 50 rpm and rougher run. One interesting note, one "cold" mourning 1700 rpm was achieved.

I am new to diesels but have significant experience with gas and I think the problem is similar to a gas engine that is simply running way to rich, not enough air for the amount of fuel being used.

I am a bit perplexed by both engines behaving in he same manner. Because of this I should share that I have installed the RACOR CCV system to reduce the oil leak/ vapor problem as descibed by several site members but with one mistake, I overlooked the crankcase ventilation vent on the back of both engines so the system doesn't create the vacumn in the crankcase, but I don't see how this could cause the problem. Filters were sized for 450 hp.
Also fuel is old about 2.5 years. I had it pumped out of the boat into a fuel truck and run through filters while pumping it back into the tanks. Gen set is brand new runs great on same fuel with no smoke.

A secondary problem is a transmision leak(Allison m20s). Changed the oil and filters and found the port engine would not go into gear after a 4 week down time and one three hour cruise. Added about two qts and everything was fine, but cannot see any leaks, suspect a slow leak that is hidden. Is there seals or a pan in the bottom that could be doing this? Suggestions?


Based on what I have seen on this site some of you know these engines inside and out, so please give me some places to start!

Thanks!

JCG

 

[Brian Degulis]

I would suspect fouled props or dirty bottom it doesn't take much to overload. If not that I would check for proper air supply run with hatches open and se if there is any diffrence. last I would check prop condition diameter and pitch.

Brian

 

[Boss Lady]

You said that the filters were sized for 450 HP. How many cubic feet of air per minute do they flow? You can't size these filters based upon HP ratings of a gas motor. The Detroit flows considerably more air. My 8v82s flow 2000 CFM each. So the filters have to flow at least 1000 CFM x 2=2000. Your 8v71ti's will be almost the same flow. Black smoke is caused by the lack of air for combustion. I would check these before doing anything else.

Max rpm 2350
Cruise rpm 1900 (this is not absolute, just the normal stated continuous rpm)

Redneck test. Take the filter elements off and see if the problem goes away. If it does, then your new filters are too small.

 

[SKYCHENEY]

It does sound like an air restriction. Are the intercoolers clean? Turbo dragging and not spooling up? Fuel filters clean? I'm just throwing out some ideas here.

It could also be something as simple as a throttle delay that is out of adjustment. Probably a full tuneup is in order since they have been sitting for some time.

 

[Angela]

This SAME thing recently happened to us. Could not push the engine over 1600 rpm and more throttle merely made black smoke pour out the exhaust. We thought it was a turbo issue, and then an air issue, but we found all of that to be in good order- no air leaks, turbos spun easily.

So, we turned our attention to fuel. We changed the secondary elements, filled the cannister up with Diesel Kleen and took her out for a ride and what a ride it was! No black smoke and we got the old girl up on plane! If you haven't replaced your secondary filters, try that. It's cheap. The elements were $7.85 each from DD. And pour Diesel Kleen, undiluted, into the filter before you put it back on. It's a cheap diagnosis to perform and will do a good cleaning on your injectors, if it doesn't solve your problem.

 

[BUSTER]

A lot of good suggestions concerning your inability to turn up your engine RPM's.Concerning your transmission oil use,if there are no apparent leaks,look at your gear-oil cooler.

 

[REBrueckner]

JCG,
Some suggestions...one question...

Each of the above suggestions is RIGHT ON. This is a great forum!!
make a checklist and check the easiest items first....

If I recall, 2 cycle Detroits required twice the air flow of four cycle diesels as sized by RAC0R CCV air filters...check that!! Think air,fuel or load as causes for smoke...likely a common problem for both engines is accessories...like filters...no a serious mechanical condition. Your emergency engine air shut downs aren't partially closed?? That's the only other thing I can think of.
If vibration is not evident at the stern, likely it's not fouled props.


Needless to say DO NOT RUN THE ENGINES AT SPEEDS WHICH PRODUCE ROUGH OPERATION AND BLACK SMOKE..NEVER,NEVER,NEVER!!!

Although you might not think so, dirty filters can both cause black smoke and rough running...

For comparison, I run a 48 Hatteras YF with 1972 8V71TI's at 435HP. They will turn to only 2125 or so RPM (max) and one engine has recent pistons/liners/valve adjustments. So I assume my props are now a touch big as the boat is heaver than when new...junk aboard and water weight,etc.

In any case these engines run clean, no smoke when warm. At start, these modest HP/displacement engines DO smoke initially, no getting around it, but not nearly as bad as the newer 6-71TI's at 485HP (and BIG injectors). It's just too much fuel for clean combustion. I can clear up smoke when engines are cold just by putting one in forward the other in reverse at the marina...they'll warm up faster too. It uses more HP than in neutral at any given RPM....At WOT, for tests, I do get a bit of temperature creep, for reasons discussed in Brian's thread on engine efficiency.

You posted:
",,,but with one mistake, I overlooked the crankcase ventilation vent on the back of both engines so the system doesn't create the vacumn in the crankcase, but I don't see how this could cause the problem..."

Is this the 1.5" air vent/pipe connection on the starboard top side of the engine, beside the aft end of the valve cover?? That should be connected to the CCV piping. If that's not it, then I may have missed whatever it is as well!!!!

 

[Nonchalant1]

Black smoke = incomplete combustion. It's likely an air restriction or a turbo or blower problem. Since you recently changed the filtration system, I'd bet on that. Run them with nothing on the front of the turbo intake so it can pull air in directly. If the filters or anything were slowing the air supply, that'll prove it. But BE CAREFULL that nothing can get in front of that turbo when it's open and running!

If that doesn't do it, check the bottom and props. If you get enough green hair and barnacles, the drag will keep you from getting your RPMs up enough to burn the amount of fuel being supplied at open throttle and that'll produce black smoke.

Doug Shuman

 

[JCG]

Thanks for the comments. this is my check list!

1. Bottom growth- don't think this is the problem because the engines did this on our first run from Pensacola to Orange Beach with a freshly painted bottom. I made the trip at 1000 rpm and then tried to put her on plane , when the smoke came I just backed off.
2. Air filters ?- This may be the culprit. I think I used the filters suggested by K&N for 450 HP, never thought about a two cycle pulling twice the air volume. Sounds like pulling the filters off and making a short run would answer alot of questions. Great idea!
3. Filters definitely need to be changed both primaries and secondary- Diesel Kleen the injectors
4. Turbos spooling up? How can you tell? I think I have seen them with the filters pulled and I recall spinning one of them by hand but not a real check of all four.
5. Emergency shutoff air gate...... don't know about this one
6. Intercoolers??? this too could be a problem. The engine room was pretty dirty, perhaps they need to be cleaned. I understand thier purpose but to be honest I not sure of exactly where they are. I believe they are in a box that the turbos blow air into and coolant water appears to be pumped into right above the blower housing toward the rear of the engine? If I am correct pulling them doesn't appear to be bad. Where do you get gaskets, seals etc?

7. Question on Racor CCV mistake, the vent I missed was in the back of the engine up high on the right side when viewing the engine from the rear. This vent is desribed in the DD manual as a crankcase vent. I noticed it while reading the operator's manual on periodic maintenance. I made three connections, left valve cover, right valve cover, and a vent pipe from something??? I need to go look at this in detail to make sure I give you good information.. I'm 250 miles away from the boat and doing this from memory.

Thanks for your help, I'll post my progress along with a bunch of questions. This site and it's members are great!

 

[BUSTER]

Concerning the air-box doos for the emergency shutdown: I don't see many Detroits anymore,but I can distinctly remember a guy in Montauk that approached me with the same problem with his 50-C. As it turned out his nephew pulled both emergency stops while at cruise speed "unbeknownst to the captain" The engines ran well at low speed but wouldn't crank up. When the kid pulled the emewrgency stops he told no one, so when I got on the boat I noticed the doors catches shut,reset them and the boat ran fine.After the tournament we lifted the blowers and replaced the two BENT air-box doors,bent just enough to allow the engines to run.

 

[SKYCHENEY]

I believe your engine would need a CCV6000. If you bought a smaller unit, that may be a problem, but not what is causing the black smoke. The intercoolers are indeed where you spoke of. Gaskets can be obtained from you local DD dealer. Where are you located?

With the other information you have provided, I would start by changing all fuel filters. If that does not do the trick, then pull the air filters and make sure you are not restricted there. I doubt a CCV would cause the problem. You are not pulling most of your air from there, just creating a small vacuum. Your air volume comes through the filters themselves, not the CCV. What filters do you have? Racor, K&N, OEM cans?

 

[REBrueckner]

So the crankcase vent up high on the right as viewed from the rear is the one you originally missed?? That's the one I described in my post....That's one of the three connections I recall making to the CCV system on each engine....plus the valve covers....

The emergency air shutdowns should be locked, fully open via small latch mechanism where the airbox intake is on normally aspirated engines....top of the engine where the turbos blow in air...These are usually either full open or snap shut when released..but a defective spring mechanism could cause them to lodge in a partially open position...but it's unlikely this would have happended on BOTH engines...yet it takes only a glance to check once you find the location.

 

[JCG]

It's been a while since I posted anything, but I am still having trouble with the engines.

I have removed the air filters, replaced main RACOR
fuel strainers, final fuel filters and I get the same black smoke......however the boat has been in the water almost one year and a good bottom cleaning is in order.

Will clean bottom and props, and try again, but suspect the intercoolers are clogged. I am reluctant to attack them for the lack of parts......Any suggestions on dealers in the Montgomery AL area, or Orange Beach?

 

[Diver Down]

I just finished a thorough cleaning of my intercoolers and I recommend you read some of the previous posts on this forum for chemical cleaning instructions. The intercooler gaskets (4 for each engine) should be fairly easy to find in LA (lower AL). If not available locally, try Diesel Specialists (www.dieselpartsdirect.com). I've found the parts guys at this place to be very helpful.

 

[Traveler 45C]

Any suggestions on dealers in the Montgomery AL area, or Orange Beach?

These guys are in Orange Beach and are great to work with: Saunders Yachtworks, 27075 Marina Road, Orange Beach, AL 36561. Phone: (251) 981-3700
http://saunders.pcmac.org/websites/SaundersYacht/SaundersYacht/Index.asp

 

[E Z Livin]

Trans oil pump seal leaking back into engine

The trans oil pump seal is leaking back into your engine. I had the same situation and I replaced the trans pump and have not added oil in 2 years.

E Z Livin

Some of you may remember some of my post on reworking a 46 ft Hatteras sportfisher. We'll she's in the water and we have started running her some and have found that the engines need some work.

The main problem is they will not turn up to higher rpm. Based on my research on this site WOT should be arround 2100 - 2200 rpm?, cruise would be 1800 rpm or so. Also, when attempting higher speeds both engines pour out deep black smoke and start running rough. Both engines crank easily, produce a cloud of bluish smoke when cranked cold for a second or two which rapidly clears up to just a hint of blue smoke for several minutes then dissipates to no smoke when engines reach about 150 degrees. Engines idle well @ 650 rpm, start instantly when warm, and run great as throttles are advanced. The problem with black smoke begin when the rpm gets to about 1500 rpm. From this point on additional throttle results in more black smoke and maybe another 50 rpm and rougher run. One interesting note, one "cold" mourning 1700 rpm was achieved.

I am new to diesels but have significant experience with gas and I think the problem is similar to a gas engine that is simply running way to rich, not enough air for the amount of fuel being used.

I am a bit perplexed by both engines behaving in he same manner. Because of this I should share that I have installed the RACOR CCV system to reduce the oil leak/ vapor problem as descibed by several site members but with one mistake, I overlooked the crankcase ventilation vent on the back of both engines so the system doesn't create the vacumn in the crankcase, but I don't see how this could cause the problem. Filters were sized for 450 hp.
Also fuel is old about 2.5 years. I had it pumped out of the boat into a fuel truck and run through filters while pumping it back into the tanks. Gen set is brand new runs great on same fuel with no smoke.

A secondary problem is a transmision leak(Allison m20s). Changed the oil and filters and found the port engine would not go into gear after a 4 week down time and one three hour cruise. Added about two qts and everything was fine, but cannot see any leaks, suspect a slow leak that is hidden. Is there seals or a pan in the bottom that could be doing this? Suggestions?


Based on what I have seen on this site some of you know these engines inside and out, so please give me some places to start!

Thanks!

JCG

 

[Nonchalant1]

There's a Detroit Diesel service operation at:

W W Williams, Southeast, Inc.
1350 Emory Folmar Drive
Montgomery, AL US 36104

Phone: 334-279-6083

The only "parts" you'll need are new gaskets. Intercoolers are easy to get on and off, but somewhat of a hassle to take apart and reassemble due to the high bolt count, like 60 bolts. They get clogged on the water side more easily than the air side, but when you take them apart you can see the fins to clean them out.

However, you had another thread about "emergency shutdown doors" not on your engines. Before you mess with your intercoolers, make sure those air doors are open and operating OK. "Black smoke = Incomplete combustion" so if your air doors are partially shut, you can't get enough air to match a full rack of fuel. Start by finding that little spring loaded lever and making sure the catch holds it all the way open. If you have to, tie it off with a zip-tie to hold it all the way open (against the spring pressure) just for one run to see if that fixes it.

Doug Shuman