"Forgot" to re-set hour meter after rebuild?

Looking at a 60+ footer that's for sale. She has twin 12-71TDs. The hour-meters show over 5000 hours, which as I understand it puts the engines well past major overhaul time. The broker claims that she had both engines overhauled about 3 years ago, to the tune of over $40k. But somehow they "neglected" to reset the hour meters. Does his explanation make any sense? I have my doubts. What do you engine Gurus think?

Personally I wouldn't expect the meters reset, I'd just expect documentation of how many hours they had at overhaul so I'd know how many it's been since.

On mine I was told one meter was replaced, the other was not. So I have original and rebuild hours. Kinda neat. The paperwork more than supports all this.

IMO, the logs should show actual hours and the time of significant maintenance performed...whatever that means to you.

In aviation, records reqts are much more precise.

Hang on. Are these engines "well past their major overhaul" at 5000 hours?

Seems awfully low.

Bobby Lex said:

Looking at a 60+ footer that's for sale. She has twin 12-71TDs. The hour-meters show over 5000 hours, which as I understand it puts the engines well past major overhaul time.

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If that's correct that's pretty poor.

What HP?
Many different variants, higher HP ones that are driven hard that 5000 could be correct.

Well maintained low HP models should last considerably longer.

Owner should produce invoices showing work done, by whom, and dates. From dates, can usually tell if number of hours make sense.

If they can not produce that paperwork, got to assume that they were not rebuilt.

12-71 can go well over 5000hrs if run easy. High output, run hard, maybe 2500.

I have 4600hrs each on a pair of mini Yanmars that are still purring like kittens with only regular maintenance items.

Ski in NC said:

Owner should produce invoices showing work done, by whom, and dates. From dates, can usually tell if number of hours make sense.

If they can not produce that paperwork, got to assume that they were not rebuilt.

12-71 can go well over 5000hrs if run easy. High output, run hard, maybe 2500.

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Yes, sight the bills.
Not even sure you can "wind back" the hours/Hobbs meters. Rebuild is 3 years ago, engines were failing somewhere short of 5000. But where?
Remember, 5000 hours is on everything, not just engines.

I’m speculating due to a lack of data. I’m going to assume a Hatteras 60’ sport fisher which could easily wear out a pair of dd12-71’s in 5,000 hours., however I would be suspicious of a complete overhaul for just $40,000. So now I’m speculating that we are talking about a 60’ semi-planning hull that after 5,000 hours of running hard got hot and did some damage. Several liners and rods were replaced and the bill came to $40,000. Major repair but not exactly a full rebuild.

Like Ski, I would like to see the engine repair paper work.

tiltrider1 said:

I’m speculating due to a lack of data. I’m going to assume a Hatteras 60’ sport fisher which could easily wear out a pair of dd12-71’s in 5,000 hours., however I would be suspicious of a complete overhaul for just $40,000. So now I’m speculating that we are talking about a 60’ semi-planning hull that after 5,000 hours of running hard got hot and did some damage. Several liners and rods were replaced and the bill came to $40,000. Major repair but not exactly a full rebuild.

Like Ski, I would like to see the engine repair paper work.

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Saw several of this type of thing online when looking
Always avoided due to engine size 650hp x 2
Never realised they were a "hand grenade" engine.

Glad we held out for a 350hp boat with an engine type that regularly get 30,000+ hours between in frame rebuilds.

I would not be afraid of Detroits with 5000 hours that had not been run on the pins for that time. The problem is figuring out how they have been run...

The only way to know the condition of the engines is an engine survey by a REAL Detroit Diesel marine mechanic.
$40 thousand is cheap for rebuilding 2 12v71s. I've been running 12v71s since the mid 1960s, off an on. A twin turbo engine gets between 2000 and 10,000 hours between overhauls, depending on how hard they are run and how well maintained. A natural can go decades.
Owners don't always tell brokers the whole story and some brokers choose not to tell the whole story.

You can’t “reset” Hobbs meters, you replace them with new and document that fact in the maintenance log.

I'll pile on in agreeing that they need to produce comprehensive receipts, work done and itemized parts. Running and maintenance logs would tell a very important part of the tale. What horsepower are those engines? They can last for many many 1000's of hours if in the common 650HP range and run responsibly.

Absolutely get an experienced Detroit mechanic to do a complete survey. That will validate (or not) whatever is being represented. $40,000 would be in the normal price range to completely overhaul a ONE 12 cylinder Detroit. Pretty cheap price for getting an essentially brand new engine.

In the meantime, see if you can arrange to have them start the engines for you first thing in the morning when they are cold to the touch. How much smoke comes out the exhaust and for how long is pretty telling. Over on the Hatteras Owners Forum, there are a lot of knowledgeable owners of these engines, plus a sticky post by one called "30 second compression test".

We have over 5k hrs on our 650hp 12-71s and they are still going strong. Two years ago all 24 cylinders were within specs for compression at time of purchase, they start as soon as the button is pushed with no smoking. After resealing the air box covers and replacing the front main seal on one they do not leak oil, however since we run at 1050rpm they will “slobber” a black mixture of soot and unburned fuel. This can be alleviated by coming up on plane once in a while and getting up to full temperature to burn it off. They will then make an amazing amount of smoke for a few minutes before clearing up.

Our hour meters are both inop so we now keep track of oil changes with the clocks on the flo-scans. These are nearly indestructible engines unless run at WOT for hours on end such as in a sportfisher. Remember: modern computer controlled engines need electricity to run, Detroit’s need electricity to shut down, I know which I prefer!

Ask for paperwork to back it, one mans "rebuild" might be a set of gaskets and a paint job. Another might include an inframe, another might be a full removal of the block and machine work to everything. If they can not produce the paperwork I would question if it ever happened, as if your to drop 20-40k on something you keep the paperwork knowing its going to add value when its time to sell.

Now lets say the paperwork was in a car that was stolen or some other story. Find a 2-stroke guy and pay for the full engine survey. Or if the boat is in good shape and your willing to gamble.... I would not be afraid of a 12V with 5k on the clock if it did not smoke a ton when fired up, did not over heat, looked neat, and worked well under full load.

What kind of hour meters? I have Hobbs, permanently reading ~1500 hours. That is the no of hours between buying the boat and re-powering. On buying the boat one tach hour meter read ~3000, the other, way less, but not functional, so I added the Hobbs pair, external to the tachs.
I also have the hour meters in the tachometers that came with the new engines (the old ones went out with the old engines). When I re-Powered, the new engines had ~1500 hours, close to the same on both. I didn't get replacement tachs for the flybridge right away, as I had to hunt for a pair of used to avoid the price of new. Those had far different readings, though both less than 1500. So now I have 6 hour meters. When I sell this boat, I doubt any broker will get the whole story, as I expect her/his eyes would glaze over long before the full explanation was done. Any purchaser relying on the broker will be confused, and will need to rely on the log book and an engine survey for an indication of the real age of the engines.
My log book details the true history of the engines, though I know that keeping close track of hours between major log entries is often overlooked in the heat of the purchasing moment.

Bobby Lex said:

Looking at a 60+ footer that's for sale. She has twin 12-71TDs. The hour-meters show over 5000 hours, which as I understand it puts the engines well past major overhaul time. The broker claims that she had both engines overhauled about 3 years ago, to the tune of over $40k. But somehow they "neglected" to reset the hour meters. Does his explanation make any sense? I have my doubts. What do you engine Gurus think?

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The invoice from the rebuilder I might believe. Reset hour meters without the rebuild invoice I would NOT accept.

I,ll chime in too.
Different engine, single, smaller boat but on third meter,Hobbs. The meter changes are in the log book in BIG notes in the place, date, they were changed. Also on the notes section divider so easily seen.

Documentation of the rebuilds is needed, a must. There is a wide variation in opinions about what constitutes a "rebuild" and one person's rebuild is another's repair . Not the same.

A large part of the expense can be due to poor access meaning high labour charges to simply get engine access. That is NOT part of a rebuild itself so the $40k, although the job cost, does not necessarily mean the rebuild.

Get documentation. Get a known DD mechanic to look at the invoices and check the engines.

Simi 60 said:

Saw several of this type of thing online when looking
Always avoided due to engine size 650hp x 2
Never realised they were a "hand grenade" engine.

Glad we held out for a 350hp boat with an engine type that regularly get 30,000+ hours between in frame rebuilds.

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650hp out of 852 cu in is no hand grenade: any engine will have a shortened life if run at WOT constantly. A 6-71 at 310hp is considered to be one of the best and longest lived engines ever made. Getting an extra 30hp from what is essentially a pair of them on a single block is not much of a stretch.

Mine have over 5000 hrs and still have compression on all 24 cylinders within factory specs. They start instantly with no smoke and do not burn oil. Careful sealing of the air box covers will stop most oil leaks. Yes, they are noisy and yes they are crude old technology: like a sledgehammer.

Any salesman saying they forgot to reset the meter doesn't know what he is talking about. You need to do independent research.

RonR said:

Ask for paperwork to back it, one mans "rebuild" might be a set of gaskets and a paint job. Another might include an inframe, another might be a full removal of the block and machine work to everything. .

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Agree. I doubt anyone spent 40K without a detailed invoice. If lost, I would request the name of the shop that did the rebuild.

Hi Bobby Lex. You're the original poster of this thread. Hope you've gotten the info needed to help you make your next move on this boat. Any further documentation from the seller on the engine work, hours, etc?

"Rebuild and Hour Meters"

As a broker dealing quite often with older boats when the sellers tell me the "engines are rebuilt" I insist on the documentation otherwise it's presented as "allegedly rebuilt". It's amazing at what some folks consider "rebuilt"! Amazingly in an effort to "cut costs" on a rebuild often folks will "leave the meters and make a note of when the work was completed."So the hour meters show the hours on the vessel, not the engines. Many of the brands have a meter on or near the engine itself and another at the helms. Paperwork with actual parts is the best, not just the last page showing "total paid". Then again with the average of the recreational fleet being 30+ years old a lot gets lost over time.
New Hobbs meters can be energized so you can run up as many or as few hours as you want.
Now for a few years Sea Ray and other manufacturers had the meters wired so that the hour meters ran with the keys energized even though the engines were not running so you would get an abnormally high number of hours on the engines.

RonB said,

Ask for paperwork to back it, one mans "rebuild" might be a set of gaskets and a paint job.

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Hear, hear. One boat I looked at had a 6LX Gardner in it, which looked excellent from the ER hatch and was described as a "full rebuild" only a couple of years before, but which in reality was a skilful paint job—it was clear that the heads had never been off this engine (so not even gaskets)!

I have to say that I have become a bit cynical in this regard, now on my 4th boat over 30'. I keep a hand-written log in a bound journal on Seabiscuit (can't get to Anika J: she's locked down in Queensland). When I sell Seabiscuit, anyone even skimming this journal can see exactly what's been done, and when, and it's backed up by receipts and detailed invoices.

Just WOW
I had no idea ther were that many 12-71 engines out there.
What kind of boats are they in and how much fuel do they burn?

Woodland Hills said:

650hp out of 852 cu in is no hand grenade: .any engine will have a shortened life if run at WOT constantly. A 6-71 at 310hp is considered to be one of the best and longest lived engines ever made. Getting an extra 30hp from what is essentially a pair of them on a single block is not much of a stretch.

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It is if its compared to 350hp coming out of 855 cu in.
And these engines , I would think, get run pretty hard in mines, logging and work boats yet still regularly, so I am told, go 30,000 hours between rebuilds - 5000 hours to my way of thinking is barely broken in.

According to wiki, a 6-72 is 426 cu in and 170hp
Double that makes 852 cu in and 340hp. NOT 650hp
At 852 cu in and 340hp they undoubtedly would and do have great longevity

Doing whatever they did to get an extra 300 horses and then whipping those extra horses clearly is a problem if 5000ish hours is considered a reasonable life.


https://en.m.wikipedia.org/wiki/Detroit_Diesel_Series_71#Variants

Simi 60 said:

It is if its compared to 350hp coming out of 855 cu in.
And these engines , I would think, get run pretty hard in mines, logging and work boats yet still regularly, so I am told, go 30,000 hours between rebuilds - 5000 hours to my way of thinking is barely broken in.

According to wiki, a 6-72 is 426 cu in and 170hp
Double that makes 852 cu in and 340hp. NOT 650hp
At 852 cu in and 340hp they undoubtedly would and do have great longevity

Doing whatever they did to get an extra 300 horses and then whipping those extra horses clearly is a problem if 5000ish hours is considered a reasonable life.


https://en.m.wikipedia.org/wiki/Detroit_Diesel_Series_71#Variants

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You are referring to a NA 6-71. A turbo intercooled 6-71 is 310hp and is still a very long lived and reliable engine. It’s only when you get to the turbo intercooled+aftercooled versions that are 435 hp that they are grenades. And even then it depends on how much of that hp you take from them.

A Detroit turbo does not produce any boost below 1500 or so rpm and a turbo engine has a lower static compression ratio than a NA engine (17:1 vs 18:1). So one could argue that at a hull speed rpm of 1050 my turbo intercooled 12-71TI is running at less stress than the NA version. After all they are making the same hp and burning the same amount of fuel of run at the same low RPM.

The same applies to the 6-71: the NA motor runs a higher compression ratio than the turbo motor. So if a 6-71N has a given life, then a 6-71 TI or even a TIA run at the same low hp level will have similar. Unless it is routinely run at high rpm/boost/hp levels, in which case the higher the hp, the shorter the lifer.

If you are going to get 30,000 hours out of any engine you are going to start it and run it for days or weeks on end, like in pump, generator and workboat usage. Not run it as a recreational boat with startup wear every day, run only 4 to 10 hours at a time and long periods of no use at all. 5000 hours over 30 years is less than 3 hours a day on average, obviously my engine was not started and run every day for 3hrs. But it was started and then cooled for a complete heat cycle many, many more times than any 30,000hr engine and it’s the cycles that affect ring tension and thus compression. It’s also the start from zero oil pressure that wears plain bearings and cylinder walls.

Not knowing how the first and second owners of my motors used them, I’ve spoken to the third and fourth: what rpm they cruised them at and for how often and for how long, I’m quite pleased with my 5000+ hours and no doubt I will be just as pleased at 6000+ in another couple of years.

Yes get the maintenance logs and invoices if available. When I bought the boat their were logs back to 2007 but no invoices. Since purchase I have full detail of maintenance, pics of invoices and also what work I have done. Additionally I have tracked fuel use and engine hrs between fill up.