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8v53 sound: what to expect?

pietro

Contributing Member
I am on the track for buying a 38" pilot lobster boat and I was aboard for a visit. Asked to have the two 1969 natural DD 8V53 and they run but in a pulsing was, 8 mean they do "vroommm......vroommm.....vroommm" instead of a continuous "vrrroooooooooommmmmmm". I let the engines run at something higher then idle, and they run fine, but once at idle they began to "pulse" again. What is it? Maybe fuel or air intake problem? Is it regular?
Tanks you all
 
dear marv, it's a pleasure to find you again.
I have found on youtube the exact example of what I am talkin about.
please take a look and hera the sound:
http://www.youtube.com/watch?v=EnN1i9LjAw0&feature=player_embedded#!
the engine seems to pulse at idle.
you gave three possible mechanical causes, but it is common that this behavior is of both the engines?
by the way, I owned a boat with 2 DD6V92TA, and they did the same sound with cold ignition for about 10 seconds, then the sound went regular.
these two 8v53n go on pulsing after 5 minutes ad idle
thank you
 
Hi pietro,

marv may have a different opinion, and I know from reading his posts that he knows his stuff.

But here's mine for what it's worth:

That sound or "idle pulse" is what we old Detroit wrenches call hunting. When it is that pronounced, it is typically caused by an improperly set or worn fuel control rack. Detroit Diesel uses a "buffer" screw that is is adjusted as a last step in a tune up to eliminate mild cases of hunting but what is depicted in the video is something I believe you would want addressed before closing escrow on a vessel.

Good luck.
 
hi jgmo,
I post to you the same question I posted to marv: why on both engines? Let me give some more details. The boat comes form an auction from a shipyard bankrupt. Some invoice told by the owner tells both the engines were rebuilt in 2009, and since then they sat till last december.
The guy that drove the boat from its original mouring to today's one (100 miles) says the boat ran very good, but you know... I visit the boat last week, asked the guy to run the engine at mouring, no load: right engine started at once, "hunting" and a little grey smoking, and kept on hunting and smoking after running at idle for some minutes. Left engine started after 6-7 seconds, and did the same of the right one. I asked the guy to put some rpm on them and let they run, he did so, 1000 rpm for a couple of minutes, always a little grey smoke from both engines, then backed idel again, and hunting again. Since the boat was not mainteined for several years, maybe is something concerning fuel circuit before injection like filters, pipes or so on?
 
That's a lot of sitting. There are three types of smoke: White, which is unburned, vaporized fuel. Black, which is partially burned fuel. And blue, which is engine oil. One other possibility is steam, which is white, and is water/coolant vapor. I suspect your "grey" smoke is engine oil and that would concern me if I were you.

"Rebuilt engine" is a relative term and can mean 1,000 things to 1,000 people. If you have a bill of services or materials, that is good but probably doesn't tell the whole story of what was or wasn't done during the "rebuild" and certainly doesn't shed any light on the expertise of the people involved in doing the work.

The fact that the boat did a 100 mile trip with a good report at the end would indicate that the engines are probably sound and that, perhaps, your "grey" smoke is occurring because the piston rings and cylinder liners may have pitted a bit while sitting and may wear back in with more use.

Why both engines? Well, they were both probably set up by the same guy and, like I said, you don't know how good he was/is at tuning a Detroit Diesel. I don't know the 53 myself so there may be some things that marv could cover with you that are specific to those that I may be unaware of... having only experience with the 71, 92, Series 50 and Series 60 engines.

Here's a story I heard while attending my first 71 tune up class over 35 years ago:

There's an American bus company called Greyhound that used Detroit Diesel engines exclusively for many, many years. Their engines always had a distinct sound while sitting at idle and, at one time, almost anyone in America was familiar with the "rump-rump-rump" of the bus while it sat at stop lights and bus stops. That sound was the "hunt" we are talking about now.

When the tune-up instructor mentioned that distinctive sound during his explanation of how the buffer screw worked on a Detroit Diesel, every mechanic in that class nodded his head that he had heard it but none of us knew why it was that all of those engines made the same sound.

The instructor went on to explain:

Someone in the bus company discovered that, other than compensating for the governor "hunting" at idle, the buffer screw really had no effect on how the engine performed. They also discovered that the use of the buffer screw caused the engine to use a small additional amount of fuel keeping the idle stable. So, they reasoned, if they didn't use the buffer screw, they could save a considerable amount of diesel, company wide, since all of the buses spent many hours per year idling in terminals and rest stops. We're talking many thousands of gallons per year.

They contacted Detroit Diesel and asked if eliminating the buffer screw would cause any harm to the engine. Detroit Diesel answered no, it would not. So, a corporate decision was made to eliminate them and subsequently, a whole continent got used to the sound of the Greyhound bus sitting and grunting and "hunting".

That was when I learned that you could actually have a smooth idling engine, without the buffer screw, if you "ran the rack" correctly and used matched sets of injectors. All the time I spent tuning those babies up, I strove to have a smooth idle prior to setting the buffer. I was usually successful and would only need to "buffer" a small amount to compensate idle fuel delivery from each injector. Obviously, the old Grayhound mechanics didn't use matched injectors or pay close attention to the rack settings.

So, things to look for are;

Exhaust valve adjustment. Improperly set valves could cause this particularly if the adjustments are different for several cylinders.

Injector height. Same thing as exhaust adjustment. If the injectors were timed "willy nilly" and aren't all the same height, then the ignition timing will be off and the idle won't "settle down" properly.

Do these engines have buffer screws and are they set correctly? I have found many to have loose jamb nuts and backed off.

Are the injector sets matched for fuel volume? If the engines were rebuilt, then they would have installed reconditioned injectors and may not have gotten matched sets. There are tags on each injector that should list idle fuel volume. Depending on where you are and who you are dealing with, matched injectors can sometimes be hard to obtain.

Are the components of the governors within wear limits? Even the slightest amount of wear on fuel control components can make it difficult to get a "good tune" on one of these two-cycle engines.

Bottom line? you need to get a bit dirty or have a qualified Detroit mechanic look those babies over. Hope this helps,
jimmyd
 
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dear jgmo,
this is the mother of a replies.
thank you very much, I have enough to work on
I will post the result
 
dear jgmo and marv,
as I am going to have a running test of the boat, starting from what we have discussed above, what could I try to do testing the boat to more understand what is going on with the engines?
thank you all
 
I pretty much said my piece above. I would only add that verifying oil pressure and cooling system temperature would be high on my list of things to watch during a sea trial.
 
With both engine doing the same thing and then clearing up after running some time and getting good and worm it dont sound like you have a problem. I whould check the above things to be sure.
 
test done. left engine starts at once, a little black smoke, and then runs hunting at idle. right engine takes a couple of attempts to start, 4/5 seconds each, blowing black smoke while under ignition, then starts and runs like the left one. after having warmed for 8/10 minutes at 800 rpm, also the right engine restarted easily at first attempt. we put same fuel into the tanks, they were pretty empty, and get out of the marina, on the river. going up-hill, against the 4/5 knots flow, both engine reached 2000 rpm max, the 40 feet lobster boat (see pic) speed were about 11 knots on the gps (maybe 14/15 knots without flow), no smoke. after 15 minutes of full throttle temps were ok, 80 to 85, but suddenly the right engine drop to 1500 rpm. stop the boat, restart and no way of having more then 1500 rpm from the right engine, but no smoke, no temp, nothing strange. stop again, shift to neutral the right engine and push the throttle, and the engine screamed to 2800 rpm and higher, very easily, with a regular noise. so we decided to get back to marina, and the right engine went up and down in its rpms a few times, almost like there would be fuel problems, and this is what I am thinking: maybe that irregular running is caused by a partially stopped filter on fuel line? anyway, I have some other issues to post to you guys: for example, are 2000 rpm max a right level, or the boat needs two propellers that let the engines run higher, 2200 rpm or somewhat? the second main issue is about transmissions, that are lazy and late to get forward and reverse, but fluid pressure was ok: maybe this one a major problem to be overhauled? or there is something to be checked or done to improve the reaction time of the two transmissions? thank you guys!!!bora.jpg
 
Well, I wouldn't describe that as any lobster boat I've ever seen but, then, I guess you can use a boat any way you see fit.
As to your stbd engine, you definitely have a GOVERNOR PROBLEM. Specifically the governor riser is sticking in my opinion. And, if it is allowing the engine to go to 2800rpm, it is sticking pretty badly since the centrifugal force of the high speed weight will not move it. This can cause MAJOR engine damage from over revving and floating the valves. This would need to be corrected IMMEDIATELY prior to running the boat again on that engine.
 
dear jgmo,
thank you for your reply.
You now, here in Italy we call lobster this kind of boat, but it's pretty much a matter of terms: we definitely do not have any lobsters to catch!!!
Are you able to tell me if this correction to the governor could be an hard job and an expensive one? Does it need spare parts?
And what about the engines speed? Should 2000rpm be a cruise level? 2200rpm a full throttle one?
And what about the transmissions?
Please excuse me, but I am basing very much on you guys the decision of going on with the purchase, if ask for a price reduction or whatever....
 
Oh, that's an ITALIAN lobster boat. Now I get it. Yes! You don't CATCH lobster on that boat, you EAT lobster on that boat!

Pietro, my advice to you is that you are going to have to find a decent mechanic LOCALLY to look at that boat for you. Basing your purchase on what I (or others) here have to say, an ocean and a continent away, would not be very wise.

On the face of it, the engines sound as if they are in reasonably good shape and may provide you with good service. BUT, that starboard engine needs someone that knows what he's doing to go through the fuel control system or it won't last long in it's present condition.

As for the transmissions, I don't even care to get into that discussion. That is a whole other ballgame and, though I've overhauled a few Allisons in my time, I'm more of an engine man than a gear man.

If the engines are set to run 2200rpm no load and fall to 2000rpm full load, I would say that is definitely "in the ballpark". Really, though, I would expect them to "droop" to 1850-1900 (or so) if the boat is properly wheeled. I suspect her props may be a bit on the smallish side but, again, I'm not an expert there.

It is a BEAUTIFUL boat and I know you probably have the "FEVER" but, if I were you, and the seller is a reasonable man, I would negotiate finding and retaining the best mechanic (with Detroit Diesel experience) within a few hundred miles and get her properly appraised and/or repaired mechanically before any deal goes forward. If the seller is wise, he sill see that it will be a much easier sell to be able to show the boat and what it can do with two properly operating engines. He may be agreeable to paying for part of the inspection or including all the work as a reduction in price at the close of escrow. It's all a negotiation from here. It will, for sure, be an expense for you but you will be protected and will probably be better off in the long run. It's either that or beat the price down as low as it will go and then get the work done after the boat is in your possession. But, when you are the owner, the "BIG SURPRISE", when something major is found to be unrepairable, is the most unkindest of wounds to the old pocketbook.

I wish you luck sir and sorry I can be of no more help than what I've already offered.
 
dear jgmo,
thank you for your wise advices. you killed me, I actually have the fever, but I have my wife on mi side who keeps me on the earth!
let me go on with this adventure, I will update the forum with what will happen.
 
HA HA! That's it my man! You need a good sense of humor to be a "boat captain" and it sounds like yours is alive and well.

I hope your wife has a keen one as well.

Yes, I know the "FEVER" in all it's intimacy! I currently own 5 sailboats and one power boat so, as you might guess, I get the FEVER quite often.

The FEVER can be quite severe and quite painful and laughing at my own stupid blunders is, sometimes, all I have left since the FEVER usually takes all the MONEYS!

The fact that I still live is a testament to how tolerant my wife is and that she has a GREAT sense of humor!
Fair winds my friend.
 
Did you let engine come up temp and if so did they even out???if so no problem. If not check idle rpm mit be low.
 
sto per acquistare il lobster da te provato potrei contattarti telefonicamente per avere più dettagli visto che hai provato la barca, sapresti dirmi come si chiamava la persona con cui hai fatto la prova in acqua
ti sarei molto grato se mi rispondessi
 
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