Cummins 6CTA 450,8.3,8m

[Bill kosky]

Morning, need some assistance. 2002, 1000 hours, 5 bladed prop, diameter and pitch unknown. Inter cooler serviced and gear cooler serviced in 2012, at 750 hours, report said seriously corroded, flushing and replacement of antifreeze done 2 years ago. WOT rpm unknown or at least that is what I am being told. Hot end of turbo and pipe and small part of inter cooler discolored light brown from heat, impeller ,oil , filters ,serviced regularly since 2012. Fuel burn I am told at 2475 rpm, 24.1 gallons, fuel burn at 2160 is 16.7 gallons per hour. I am sorry that I do not have pictures of turbo , but when I looked at engine it was apparent, and drew my attention..

5 bladed prop pushing 19000 lbs, beam 13.6, water line 36 ft, semi displacement down east hull.

Seriously considering boat , but real apprehensive on motor, confirm or dispel my fears please .

bill

Topic

[Rob Schepis]

I know you said the aftercooler was serviced the Seaboard way but I want to make sure that included removing that core from the housing for cleaning of water and air sides and then reassembly the Seaboard way.

As to the fitting breaking off, that’s not “unprofessional”, that was the gear cooler’s way of telling you that it is done. The fitting was weak because it is eaten away. Probably the original cooler and no zinc? Any competent mechanic could get that fitting out and clean up the threads and install a new fitting, JB Weld as pipe dope if needed BUT that is playing with fire. Keep in mind, that gear cooler is seeing 300+++ psi on the gear side which is up against almost no psi on the water side. Much different than the other coolers on the engine. Play it safe and smart and look into replacing that cooler.

[George Samaha]

Broke a hose barb in the gear-oil cooler…

While waiting to get the bottom cleaned and do proper RPM and WOT testing, we are checking the saltwater side. Got the STBD aftercooler core out, it was 80% blocked (see attached)! We cleaned it and will put it back the Seaboard way then pressure-test.

But we had a problem, there is a hose barb nozzle in the gear oil cooler that broke off (so unprofessional I know.. or should I say lucky we caught it?) see the second picture. This is a seawater output that goes to the dripless shaft seals. Is there a way we can weld it back or maybe tap for a new nozzle in there? Is this bronze?

1 user thanked author for this post.

worldcatlemon

[Rob Schepis]

You’re welcome. No there is no way to measure it on a mechanical engine without adding aftermarket systems, such as FloScan and others.

Once you get the prop load within spec you will put the engines in as close to a “test cell” environment as possible and then the printed fuel burn curve and chart from Cummins will be your accurate guide. Until then you are “off the charts”.

[George Samaha]

Thanks for the details, BTW I was always confused about WOT being at neutral or not. Now it is clear, will do as you suggest. Is there a way to measure GPH on these engines? How the manufacturers do it on the newer engines?

[Rob Schepis]

Verify Those Tachs

Okay, sounds good. Let’s move on to step #2 since there is no better time than the present and the sea trial with someone else running the boat is ideal.

On the next sea trial you need to get a handle on the accuracy (or inaccuracy) of the tachs. A little cumbersome to do when alone but a pc of cake with a couple three guys on board. Does your gasser marine mechanic have a laser photo-tach in his tool bag? If not, get one. Or even if he does, get one for yourself. They are cheap enough and a good tool for down the road. Mine has gotten me a whole bunch of free boat rides and beers. The other item you need on board at all times is safety ear muffs. Ever sat alongside a diesel when it’s running at high rpm?

I always prefer to do the tach check by riding in the engine room but not all conditions allow this and you do need a third guy for signaling between you and the operator. If the helm tachs have a nice steady reading then you can do the tach check at rest. Some tachs are erradatic and bounce around..

Once you’re out of the slip and have her up to full tstat operating temperature check the tachs at several increments and record the dash tach vs photo tach readings. Do something like: Idle, 1500, 2300, WOT and High Idle.

WOT will be the rpm the engine hits under full load while underway.

High Idle will be rpm the engines hit in neutral. Like I said, this should be done at full operating temperature. For high idle, bring the engines up to the mid-2000 rpm range, hold for a second or two, and then a slow and steady push to WOT just long enough to steady and get your readings at the helm and on the photo tach. Then pull back slow and steady.

Sounds a little complicated maybe but only because I explained it all in “too many words”, it’s no more than a 15-20 minute exercise.

With all of this data at hand you will be in a very good position to see how things are really setup and how things will change once you top off the tanks and fill the boat up with your all your stuff..

[George Samaha]

No, this horse will drink the water 🙂 As you said, since anyway we are going to do it, I will ask for it.

OMG look at us, it’s Christmas and we’re talking engines. Must be some kind of sickness 🙂

Merry Christmas to all those who celebrate Christmas. May you always be blessed.

[Rob Schepis]

100% your call. It’s your wallet and your blood, sweat & tears. We are just here to guide….but I will admit that guidance gets less fun when the horse doesn’t drink the water! Kidding aside, if the circumstances and numbers are such that “it is what it is” then go ahead with the deal and do it all on your watch and your dime. But your gonna have the bottom cleaned anyway… right? So why wait……

[George Samaha]

You're right Rob

Rob, you are absolutely right in everything you said, normally I would do it that way, but sometimes there are circumstances… Seller is a friend of a friend, boat is very clean for its age and the price is good (not 6 figures). I noticed the turbos from the beginning but somehow felt it was acceptable because I had seen photos similar, and, I was seduced by the low hours..

I did get a dockside inspection and got a mechanic to look at the engines. He said the engines are in a very good shape (he is an expert in marine gas engines though), he did not even mention the discoloration, so I posted the picture here to see if you guys, the experts, will raise any red flags. After sea trials, I kind of gave my word that I am buying. Now only waiting for them to prep the paperwork. So it is difficult for me to go back and say I want to clean it and test again.

But if you guys think I am making a mistake, I will do it.

[Rob Schepis]

I simply do not understand why any buyer would want to inherit a seller’s problem. An engine that falls that far short of rated rpm is no different than a windlass that won’t go up/down or a radar that won’t spin — it is in it’s on way “broken”. Wasn’t the boat short hauled as part of the inspection? Are you doing a formal pre-purchase inspection/survey? The normal m.o. is dockside inspection of all equipment and the engine room (while things are still at ambient temperature, so we don’t have to crawl around a hot engine room) and then short haul and powerwash (if needed) and then sea trial. Sometimes if it’s definitely known to need a bottom cleaning the boat is hauled and scraped/washed the afternoon before and left in the slings so the hull is dry for the surveyor in the morning.

That boat must hold 600-700 gallons of diesel and 100+ gallons of water ….. All loaded up you will be adding a good 4,000 pounds of fuel and water plus all the routine “stuff” that the family brings along. The current problem only gets worse.

A clean bottom is in no way asking too much at the time of purchase, whether it’s on your dime or his.. especially considering this must be a six figure purchase.

[George Samaha]

Happy to learn

Sure, I’m here for guidance. I am a programmer but know mechanics, new to marine and diesel and injectors and turbos though 🙂 ! was about 10yrs old when I “helped” the mechanic rebuild my father’s car engine (V8 455). At around 20yrs I rebuilt my motorcycle engine just for the fun of it. I was left with a bunch of screws but it ran well afterwards 🙂 Now in my 50’s I will not leave screws out.

Rob, thank you for pitching in. The captain is the person who takes care of the boat for the owner. He is experienced (and even knows where the zincs are located on the engine), he seems the kind of person who is too meticulous. I have a feeling he did not open the (electronic) throttle to the max, it was at about 150 degrees when we got 2200RPM. Later, when my son raised the volume on the radio, he reduced it by 2 notches as if he did not want to harm the speakers. I am in the same area so he offered his services to me if I buy it, and promised that the engines are good and that the boat will do 22 knots when the bottom is cleaned.

I am not sure we can clean the bottom before buying but the price is good even including the 15k roughly estimated repairs. So I am thinking to buy it and then start by cleaning and checking aftercoolers / turbos, then test full throttle with a good tachometer and log GPH (will install sensors if needed), then go from there. Does this sound like a good plan?

[Rob Schepis]

George,

Who was the “Captain” ? Hired by the seller or broker?

Here’s how I would proceed with this deal. Make them prove his dirty bottom comment. Have the boat lifted, bottom cleaned and do another sea trial. The target rpm is 2,700 range but if she still don’t make at least 2,600 with clean bottom and light load (you said empty tanks) the boat is not “running to spec” and compensation needs to be made, at a minimum equal to the cost of a new set of props. I think you will find that the Capt is full of it, either because he’s got vested interest in the sale or he just doesn’t know….

1 user thanked author for this post.

Tony Athens

[Tony Athens]

Grunt Work = You Provide and We Guide……………………In the end we all learn that way..

That’s always the best way for the long term as 90+% of the hired help never cares the way an owner / operator does… It’s only an income steam to him that they don’t want to end.

Tony

[George Samaha]

I Love these engines

Thank you for the fast reply Tony. You are the greatest. The boat is very clean so I think I will buy it after factoring in those costs. I fell in love with these engines, mostly from your comments on them, so I will do some grunt work with pleasure and will treat them like babies. 🙂

[Steve Lewis]

Thank you Tony

Tony,

You just answered a lingering question in the back of my mind. I never asked, but I always wondered how tolerant the 6CTA/QSC is of being over prop’d. I know that it will vary based on all sorts of conditions but what I see in the picture from George Samaha is an engine with a turbo discolored to the point of “Chocolate Pudding”. My relative scale is Vanilla – Butterscotch – Chocolate Pudding. The discoloration is proportional to the amount of “abuse” that the engine has sustained. That must be balanced against how many hours it took to discolor the turbo. My personal break point is between butterscotch and chocolate. If the turbo shows butterscotch or worse I just pass on it and move onto another boat.

The nugget of gold I just picked up on is that the 8.3 is a little more tolerant of abuse than I figured. I have seen quite a few Searay’s in the 45 foot range with the Diamond 450’s or QSC500’s with chocolate pudding colored Turbo’s and low hours(400 or less). In one case a 420 Dancer with Diamond 450’s had 250 hours and “cooked” turbos. That to me means significant abuse. Or as you call it “the nut behind the wheel”. The fact that you are indicating that at ~600 hours and the turbo is showing over propping and is pushing the Chocolate portion of my scale is not a huge concern, the attachments will need some care but the core of the engine is ok, gives me more data points in my search for a larger boat with diesels.

I have tried to read, understand and interpret the info that is presented on these forums and then use it to inform my search for the next boat. Your response to this post filled in a gap in my knowledge and will help me figure out which boats to pass on or dig in a little more……

Cheers!

Steve Lewis

[Tony Athens]

Regardless of the bottom condition, the engine (or engines) are most likely grossly over propped.. That does not mean too much a 600 hours, but assume you will spend about $12-15 K going thru props, aftercoolers etc etc etc– ( if twins)– 60% of that if a single..

If you do all the grunt work yourself to get it all up to spec, you could save 30-50% of that.

Buy it accordingly..

Tony

[George Samaha]

burned turbo?

Hi,

Thank you guys for the helpful information you spread out. I am seeing the same thing, 6CTA-8.3-M3, only 600 hours, darkened turbos and coolers on both engines. picture attached. It is a 2001 Sea Ray 400 bridge. It could not do over 19 knots / 2200RPM on sea trials, empty tanks, captain said the hull is very dirty. Actually he accelerated very slowly and took about 30 seconds to get that.

* Does this seem like a new or rebuilt engine?

* Could it be that the turbos are not working?

* What are the symptoms when the turbos are like the pictures of Monk 36’s turbos Tony posted above?

* At bottom center in the picture, is this the diesel cooler suggested to be removed? or is it the transmission cooler?

* If I buy it and want to test no load WOT what is the max RPM I should get?

Thanks,
George

[Tony Athens]

Per engine.. Less per engine is OK.

Tony

[George Felix]

Fuel burn and prop

Tony, I was reading your comments that the Cummins 6CTA8.3M should burn 13.6 gph @ 2200 rpm and then your propped correctly. I think I have that right. Sorry if this is a dumb question but is the 13.6 for both engines or per engine?

I’m looking at a 38′ Tiara Open with 800 hrs and they tell me the range is 350 mi @ 25kn 2250 rpm. Top speed 29kn @ 2500 rpm. Don’t beat me up I’m just trying to learn…:)

Also, is that the magic formula 13.6 @ 2200 or is close ok? I assume if the boat is not at this target performance you make the prop changes until you get it right which could be a process right?

Thanks for the help I promise I learn fast.

George

[FERNANDO DACOSTA]

Fuel meter

Hi Bill. I am just curious, I have a Cummins 6cta, I don’t have a fuel meter. How do you know your fu burn, did your engines came originally or did you installed a fuel meter ?

Fernando

Bill kosky wrote:

Morning, need some assistance. 2002, 1000 hours, 5 bladed prop, diameter and pitch unknown. Inter cooler serviced and gear cooler serviced in 2012, at 750 hours, report said seriously corroded, flushing and replacement of antifreeze done 2 years ago. WOT rpm unknown or at least that is what I am being told. Hot end of turbo and pipe and small part of inter cooler discolored light brown from heat, impeller ,oil , filters ,serviced regularly since 2012. Fuel burn I am told at 2475 rpm, 24.1 gallons, fuel burn at 2160 is 16.7 gallons per hour. I am sorry that I do not have pictures of turbo , but when I looked at engine it was apparent, and drew my attention..

5 bladed prop pushing 19000 lbs, beam 13.6, water line 36 ft, semi displacement down east hull.

Seriously considering boat , but real apprehensive on motor, confirm or dispel my fears please .

bill

[Tony Athens]

This attached picture should explain “Doomed to Failure ” more than any dissertation could…….A Builder design that was most likely approved by a “Cummins Application Engineer” that had his head in the sand, and the result of such a design a few years later with under 500 total engine hours…

Tony

[Author]

Replies