Winter 6-71 service?

[hcalmar]

Happy New Year!

I would appreciate some input on my origional plan to develop a maintenance base line for the DD 6-71 TI's we have in our 1979 37C. We brought the convertible down from Winthrop in November and it ran well.

Some specs: The 671-TI are Covington factory-rated for 410(crank) 390(prop) and have 800 hours since a major overhaul two owners ago. However, there is no documentation. I did not have a compression test. Starboard-RPM wot 2325, no load 2586, Port wot 2299, no load 2625 (overproped?). Engine temperatures at idle 180/180, at wot 195/188. Basically the engines ran very well at sea trial with no smoke or excessive steam noted. Smooth, crisp throttle response at all RPM ranges and after the cold ten-hour trip from Winthrop MA to Mystic CT in November, there was no oil use on the port engine and half a click between high and low on the starboard stick.

The surveyor recommended I have the racks done, add airseps,replace the impellers, replace flexible hoses ,gaskets ect., and repitch the props to achieve 2500 load rpm if setting the racks don't take care of it. There was oil leaking at the governor covers etc.

On the strong recommendation of my friends with detroits, I contacted the most reputable shop in the area. They are a great bunch and I know them to be open, and trustworthy. I asked them to give me an estimate for base line maintenance, that is, change impellers, zincs, clean heat exchangers and intercoolers, service hardware, miscellaneous hoses, remove crank breathers for cleaning and set the racks. The estimate was $1200.00 for parts, $575.00 to subcontract the heat exchanger and intercooler cleaning and 40 hours of labor at $90 hr($3,600) for a total of $5500.00. I understand it is a rough estimate. It shocked me a little bit but then I am new to diesels.

Half of my friends tell me to get it done and over with, enjoy having a baseline, avoid a problem in one of these areas next summer when it is warmer and "you're going to have to do all that work anyway, over time and it will cost you more money to do it separately". The other half of my peers point out that it ran flawlessly from Boston and suggest I have the racks done, impellers changed and zincs installed and see how things go next summer.

Personally, I am handy but don't have a great deal of time between now and May and have never worked on Detroits before. The first time around it will be nice to have someone else do the work and they have no objection if I observe them doing the work. Moreover, there are a number of other projects that need to be done, including, new carpet, shaft packing,battery changer, cutlass bearings, maybe re-prop, replace the aluminum 90 gal center tank with a holding tank and all the other miscellaneous items you would expect to have identified after a survey on a "old" boat. I know I will have plenty to do as it is.

Other than doing it all by yourself , does the estimate seem out of whack? Would you break up the jobs over time or just get it over with? I would appreciate your thoughts.

Hal

 

[Genesis]

$1200 for parts? What parts? Impellers are $100 a shot max. When you speak of hoses, are you talking about ALL engine hoses (lube oil, etc)? If so that's not an unreasonable number. If not then its WAY unreasonable. The raw water hoses are not terribly expensive or extensive. Fuel and oil hoses are another matter - if they're the Aeroquip stuff they're spendy, even if the ends are ok and can be reused.

Labor sounds about right. It takes me a man-day to do a tune-up on a pair of Detroits "by the book", assuming I'm doing nothing else. Another man-day to tear down and replace the cooler cores. Two more to do all the hoses, and one for "aw #$#@!!", which always happens.

The subcontract numbers don't seem TOO outrageous if they include ALL coolers (gear, heat exchanger, fuel and intercoolers) - those run roughly $75 each and there's eight of them at a radiator shop. So figure there's that.

You're at least a bit out of tune - you should turn 2700 no-load and 2500 WOT on those motors, and there should be a plate on the valve covers giving these numbers (unless someone has removed/lost it.) No-load numbers are low. This implies that the governor is not right. You're definitely overpropped on the port side, and probably on the starboard - can't tell for sure though until the governor's right. Oil leaks around the governor cover likely mean the last guy in there didn't replace the gasket and tore it when removing the cover - that's fscking stupid as its only a couple of bucks!

I'd get it done, given that you know there are issues. These are good motors but they're EXTREMELY intiolerant of abuse as they're pumping out a lot of ponies out of very few cubic inches. Make sure they're right and you'll be ok - run 'em overloaded and you'll wind up rebuilding them a lot sooner than you want to.

BTW expect to find at least one thing that is shot and doesn't look it, and will cost more - maybe quite a bit - of money to replace. It ALWAYS happens when you start on something like this.

Don't do Airseps - get the Racor CCV system. Airseps suck; the CCV system is no more money and a LOT better for your motors.

 

[Nick]

I have the same engines in our 37 and I would agree you should have the work done to get you a good baseline of maintenance. The cooling system service including the gear coolers is necessary; you may be surpised at what accumulates in the cooling system. Three years ago when I purchased our 37 I did similar work including all water, air, oil and fuel hoses on the engines and lots of other misc stuff to catch up on my baseline. I also changed the turboblankets, same exhaust hose and found the unknown bad turbo when inspecting the turbo and air seps. Plan for that &*%^$ kind of problem as Karl said. You may also want the exhaust shower head at the riser cleaned. The showerhead is where your raw water dumps into the exhaust elbow.

Your estimate seems reasonable; good piece of mind!

Send an email if you have any questions!

Nick

andrian1@optonline.net

 

[MikeP]

Genesis pretty much said it all - the only thing I'd add is that if you are mechanically adept, buy the DD service manual for the engine (and good quality tools if you don't already have them) and do the work yourself. They are very straightforward and as long as you do it by the book, you will be fine. That way, you know it's done properly and you have the added advantage of knowing exactly what the status of YOUR engines is (are?).

In fact, whether you plan to do the work or not, buy the DD service manual. The plot's not all that great but it's an interesting read!

 

[SeaEric]

Make it unanimous. Sounds like a reasonable proposal to me. I'd go for it and get it done.

 

[Passages]

I've always been a believer in doing the easy stuff myself and hiring help where special skills or tools are needed. Changing impellers, zincs & hoses can be done by anyone with minimal mechanical talent. Upgrading your air intake to a CCV, and cleaning your coolers can go either way. For a PROPER tune up, I call a pro.

With regard to the baseline cleaning of the coolers, I recommend removal & inspection. Read the thread on "turbo cleaning" for a peek of what may be going on in your intercoolers. After your first "out of boat" cleaning. You can then do the clean in place method described in the FAQ section.

On the other hand, if you have a spare $5500, and just want it done, by all means have your mechanic do it all.

After the above work, recheck your loaded WOT. If you can not get 2500-2550, reduce prop pitch as needed.

 

[REBrueckner]

I'd opt for the rack adjustment , impellers,zincs,etc,and other minor items suggested by some of your friends as a first step. Check the freezing point of your engine coolant. A 50% mix gives good cooling, too high a mix of antifreeze REDUCES cooling ability. Then check engine operating temperatures as described below. If the coolant hoses are cracked or hardened, definitely get them changed. A qualified tech can easily tell from look and feel which hoses may be due for a change. Test the PH of your coolant. It should be slightly alkaline (not acidic).

Although your coolers may be coming due for a cleaning if they have never been done, your actual operating experience suggests they are still ok. Especially since you don't know the impeller condition yet. Unless they get clogged with debris, they don't lose cooling ability overnight.
See if your WOT RPM changes after the rack adjustment and if not consider taking an inch or two pitch off the props. But before this, check both engines actual temperatures under load with an infrared thermometer. Check each exhaust port and record temp readings. If one port is lower temp than others, have that injector pulled. Check each stage of both salt water and fresh water cooling temps as well.
You'll not only get componenent by component temp comparisons, but can identify if any component on either engine is "on the edge" of cooling properly. For example, if the salt water cooling temp rises 15 degrees on the port engine, but 25 degrees on the starboard, it would indicate the starboard heat exchanger needs cleaning. It's very likely the on board engine instrument temp gauges read differently, they are rarely all that accurate. My starboard engine coolant temps reads almost ten degrees hotter than port, but infrared readings show they are within 3 degrees.

One more thing: If you opt for more extensive maintenance, be sure to get the turbo's checked and intercoolers cleaned. There is no need to worry about CCV's this winter.

 

[Genesis]

My personal view is that I'd do all of it myself....... that way you know its done right!

With that said, if you don't have the time then paying someone is reasonable.

Here's the thing - cooling system problems are THE reason people end up doing low-time overhauls on diesels in boats. THE reason. Everything else pales by comparison. And finding out that you've got a problem you need to fix NOW in the middle of June when you want to go boating and every mechanic has a 3-month waiting list is not fun. I went through this crap for a very simple in-warranty problem on my genset (bad injector) which I could have changed myself but doing so would have voided the remainder of my warranty. I waited more than a month for that guy to show up and do an hour's worth of work. He did the job competently, but the point is that I had no genset for a month during prime boating season.

That sucks and avoiding it is important.

Right now the water is cold and so even with severely compromised systems all will be fine. Next August this will not be the case. I can run with half water flow in 40F water and all's well - the same trick attempted in 80F water results in an instant overheat.

I am a big fan of preventive maintenance on these things. Also, be prepared for a year or two (if not more) of "catch up" - doing it all now saves you time down the road, but costs money. You choose - if you can do some of it yourself that will save bucks, and besides, you really want to learn how to do most of this stuff anyway - none of it is really very hard.

Detroit tuneups are not complicated. They must be done by the book, but they're not hard and the number of special tools required is small. The first time you do it you will swear, bang your head, and it will take quite a while to get it EXACTLY right. The second time it will be MUCH easier. The third, you can almost do it without the book. There's a "feel" to it that cannot be described but is easily learned.

The very first thing you check is the alarm systems, and you will probably want to augment them. Hatteras has historically used "combined" alarms (e.g. engine oil pressure and high temperature ring on the same light.) This IMHO sucks. Their horns have also been questionable in terms of volume in some installations.

I am a BIG FAN of separate alarm circuits for ALL critical functions. I want the following things monitored on my boat as CRITICAL items for each engine, ringing SEPARATELY:

1. Engine oil pressure.
2. Engine water temperature
3. Exhaust stack temperature (at the raw water injection elbow)

I'd also LIKE to have gear oil temperature, but I'll live without that if I can't have it - just be aware that overheated gear oil will toast a gearbox just as quickly as it will toast an engine.

All alarms must ring on a REALLY LOUD bell or horn. I mean REALLY loud! It should be audible over the engines at FULL POWER anywhere on the boat. If its not then its not loud enough. Get a louder alarm sounder or wire more than one and disperse them as required. Put a disable switch for the bell at the helm but hide it so you CANNOT shut it off accidentally and intentionally ring that sucker every time you start up so you KNOW it works.

The first two of those above are critical items for obvious reasons. Engine oil pressure should ring at 7psi, which is your "aw crap I need a new motor" alarm. Seriously - if it goes off under power you're toast - the minimum safe oil pressure under load is 30psi, but you can't set the alarm there or it will ring continually at idle. So if it goes off under load, you're toast. The second should be set for 195F - NO HIGHER UNDER ANY CIRCUMSTANCES. This one WILL warn you before damage is done provided you back off FAST if it rings and raw water flow is still happening.

The third is to keep you from catching the boat on fire, and to prevent a situation where you overheat and CAN'T cool it off. The stack alarms should be set right around 210F and are best done with a little Airpax switch - Hatteras put them on the boats, but these tend to corrode and fail, so check and make sure they work. If that alarm ever goes off SHUT DOWN NOW! It is extremely sensitive and will ring almost immediately on raw water flow loss - long before you overheat and before the inside of your fiberglass exhaust catches on fire - which it will if you ignore that alarm or it doesn't work!

Next, make sure the ER FIRE and bilge HIGH WATER alarms work. Those are critical items as well for obvious reasons.

If your boat doesn't have mechanical gauges in the engine room, add them. Oil pressure, water temperature and PYROMETERS at a minimum. Cheap and easy to add, and they give you a means to check the electrical gauges at the helm. Make sure for your oil pressure gauge you do not use the cheap automotive tygon tubing - have a hydraulic hose made up for that connection instead. Electrical gauges are notoriously unreliable.

Buy and carry an IR non-contact thermometer. Sears has them. If you ever wonder if the temperature you're seeing is REAL, this will tell you in one second flat provided you can "see" the item in question. Worth their weight in gold.

Those are good starting points. You'll almost certainly find that some of these items need attention. Its FAR cheaper to do it now than to get a nasty (and expensive) surprise down the road - trust me.

 

[Passages]

If you were to break up the project over several winters, you might want to use the following schedule:

This Winter: Zincs, Impellers, Cooling system cleaning, Tune up (spring)

Next winter: Zincs, Flush & Replace antifreeze, Replace hoses, depitch prop if needed.

3rd Winter: Zincs, Impellers, Racor CCV Air Intake system

This would take care of the most importent items first and conserve a little cash flow.

I'm on year 3 of my 6-71ti's and made some mistakes. First, I bought AirSeps on the recommendation of my mechanic. Second I waited 2 years before tearing down my cooling system only to find it scaled up beyond belief.

 

[REBrueckner]

Passages: If your engines operated ok, not overheating, did the scaling really make any difference? I mean that could have been present for ten years without impact. Of course you lose some margin of backup cooling safety during the entire period.
I had mine done at purchase because I had a cylinder kit overhaul. The heat exchangers and tranny coolers were good, but two of four turbo intercoolers were gunked up. One had to be replaced.

 

[REBrueckner]

(second post)
There's a lot of good advice and experiece evident in the posts here.
I forgot to ask earlier, what maintenance records did your get from the prior owner? That's really a starting point, assuming they have the detail to be authenticated as actually having been done. Also, did the prior owner discuss his normal cruising speed and RPM? What hours do these babies have. And I do like the post about salt water temps being cold during your delivery run...I should have thought of that.

 

[Passages]

Passages: If your engines operated ok, not overheating, did the scaling really make any difference? I mean that could have been present for ten years without impact. Of course you lose some margin of backup cooling safety during the entire period.
I had mine done at purchase because I had a cylinder kit overhaul. The heat exchangers and tranny coolers were good, but two of four turbo intercoolers were gunked up. One had to be replaced.

To my amazement, no.
The engines were running hot when I first bought the boat so I drained the main HX, filled it with white vinegar, let sit overnight and problem solved. Repeated the vinegar trick in 04. No problem through 05. Last month, when I pulled off the intercoolers , fuel & tranny coolers, they were so scaled (about 50% blocked) I was surprised they were cooling as well as they were.

 

[REBrueckner]

Someone wisely noted both your NO LOAD and WOT RPM are a bit low. The first thing (and a simple one) to check out is if your throttle linkage permits full engine activation.
With throttle controls at WOT (I think you can do this with the engines OFF), see if the fuel control arm on the engine can be moved further via direct hand pressure. Maybe the controls at one or both helms need adjusting so you can reach full RPM.

 

[Genesis]

Yep. That's entirely possible - a VERY SMALL lack of movement will translate into 100-200 RPM! You'd be shocked at how little it takes!

It MAY be something that simple. If it is, then its a 5 minute fix.

BTW, I'd get some test strips and check the coolant NOW. If its out of balance changing it NOW will be the best $100 you spend on the boat. Alternatively, if you have to BUY some silly amount of those strips (you can't find someone with a few you can have) then I'd go ahead and do the fresh water hoses and change the coolant at the same time, since you have to drain it to get them off.

 

[hcalmar]

Thanks all of you for the advice. I quess I just needed the excuse to spend all the $$. I need to follow up on the estimate, for example, the service includes only the heat x changers and intercoolers ( gaskets $296, radiator shop $575) not the fuel and tranny coolers-capitals as Karl recomends. And I realize I do not have high water alarms. I will make sure I am there for the entire service call, they encourage it, and I can learn something- that will be worth something. My other temps were:

Starboard:
riser/elbow 67idle-79wot
exhaust port 180-188idle,416-430cruise
oil 237 at filter
tranny coolers 117in/87out
intercooler air 265in/135out

Port:
riser/elbow 65idle-76wot
exhaust port 160-177idle
oil 232 at filter
tranny coolers 128in/81out
intercooler air 255in/133out

The previous owner cruised at 1900rpm, the boat and engine room are imaculate. No documentation of maintenance or the overhaul but reported to be 800 hrs smoh.

To the 37C owners- where is your holding tank and how big is it?. This boat only has a 30gal bladder but a 90 gal alluminum fuel tank centerline I will probably remove unless there is a better place for the holding. The pump is galleymade (new reman). I have a family of 5. I assume at a gallon a flush I need at least 40gal

 

[Genesis]

That looks pretty good on the specs. Note that your exhaust port numbers are going to be low, as you can't get in there where its the hottest - the manifold is water-cooled.

Put in Pyrometers - these are important if you don't have them, as they'll show you trouble early on....

 

[ADaily3224]

Hal,

If I remember correctly the holding tank is between the engines, built into the hull forward. There should be a small plywood hatch cover about even with the front of the engines. I think the capacity was about 50 gallons or so. As far as a bladder or aluminum tank? Neither are factory. I would bet you are going to find fuel in the holding tank as the 37 had small main tanks and some people converted holding to fuel. You ought to contact the person you bought the 37 from and try to get as much documentation as you can on what he did to the boat. It may save you a few dollars. I met the previous owner of mine on the sea trial, he insisted he come along. After I released the reserve, right there and then, he promised to send me all the documentation, records, etc, he didn't live up to his commitment. It's worth a try.

Tony D

 

[Nick]

Yes the holding tank is between the engines under a plywood deck and ours was jury rigged/converted to fuel just as Tony noted. I believe it is 70 gal and FRP.

Nick