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Delta_JimS 05-19-2015 09:49 PM

How common is 10K Diesel Hours
I have seen numbers tossed around from time to time, but seldom anyone post their Diesel Engine hours.
How common is 10K+ hours on the Forum boats, and what kind of hours is typical (if that can be) before an engine rebuild?

I have seen stated that 15K hours is not uncommon if the engine is not neglected or abused; even as much as 20K.

What say members? Anyone care to state they have 10K+ hours and their diesel is running as good as ever?

My '84 Volvo is just now approaching break-in at 2K hours and runs better every time out. Not sure how well she was cared for in the past, and I heard that she was mostly run at too low rpm, which may explain the constant improvement. This last weekend when I started her cold, she barely smoked at all.

TDunn 05-19-2015 10:19 PM

Our local fishermen start thinking about a rebuild or new engine around 10K hours (5-6 years). I think it all depends on how the engine is run. I have been a sailor for 45 years and you seldom see a sailboat with over 3,500-4,000 hours. The short engine runs typical of sailboats are hard on engines. That said, I have had my sailboat for 19 years and have only put about 650 hours on the engine. So to get to 10K hours I would have to own the boat for about 300 more years :).

I think that we seldom see 10K hours on a recreational boat because few people use their boats for more than a couple of hundred hours a year. So 10K hours takes a LONG time to accumulate.

Delta_JimS 05-19-2015 10:38 PM


Obviously, I see your point, and I am clearly an example with less than 2K on an '84.
But, I have been looking at some larger boats recently that have 6-8K hours and that gives me real concern. I would hate to buy into a couple of engine rebuilds in a couple of years at $20K apiece.

At over 42' it seems, a lot of older boats are clocking over 5K these days.

MYTraveler 05-19-2015 11:28 PM

Hours must be understood in the context of 4 criteria:
1)typical load -- an engine that is mostly run at more than 90% of max and more that 90% load will have a dramatically shorter life;
2) a high revving (say 3500 rpm+) will have half the life of one that maxes under 2400;
3) Total years -- hours spread over 12 years are twice as wearing as those spread over 6; and
4) naturally aspirated last at least 2x as long as turboed.
All assuming regular oil changes and good maintenance, etc.
Given those parameters, normal life expectancy will range < 1,500 hrs to 30,000 +

Tidahapah 05-19-2015 11:45 PM

Yes they all vary , depending on use and care.
My mate has 20,000 hrs on each of his Scania mains and they are going well , just blow the slightest smoke on start up . These engines have been working for 25 years.
Spoke with a cray fisherman down in Tassie a couple of months ago and he said he had just done the injectors on his Gardner 6LXB as she had 53000 hrs up and he was planing to use the boat as a cruiser now that he had retired.
And as stated by MYTraveler all his points are valid.
One of the reasons it is nice to have a slow reving naturally aspirated engine.

BryanF 05-19-2015 11:56 PM

I see fish boats around me where I am at the moment and the d343 cat that was up the way had about 15000 hours and he expected 40,000 before rebuild. 8v92 that was here was redone at 12000 because he had the time and the money not because it needed it. I have also seen 1500 hours and done.
So how many hours will it run is like asking how long is the string in this ball of string. With that said it is not uncommon to see 40 to 50 thousand hours in big diesels (say 14 liter and larger) Smaller faster turning less hours I think 10 to 15 thousand and really highly stressed stuff a lot less than that like 3000.
An example is with cummins. The little 6bt with an after cooler and all hoped up to 300 plus horse power (5.9 liter) will not last as long as the n14/ 855 cummins at 360 hp. And 14 liters displacement. I think you can generalize and say the bigger the engine mostly the longer the life under similar conditions. But loading and maintenance count for a lot.

Ski in NC 05-20-2015 12:15 AM

You can design a powerplant for long life.

You can design a powerplant for high output per pound.

They can both burn diesel. They won't be the same machines!!

hollywood8118 05-20-2015 12:16 AM

The N46 I just did a delivery on has 9000+ hrs on the clock.. and the John Deere runs like a watch. As the hours start to add up the peripherals will need to be worked on before the "engine" needs anything. I know in diesel driven water irrigation pumps the service companies would see 100,000 hours on some motors.. serviced on a strict schedule.. working in a dusty but dry environment. those motors ran the same rpm and load all the time.

I believe the N46 I was on I would feel good for at least one if not two circumnavigations.. lots of life left. The motor was tight, used almost no oil, fired up instantly, sounded great, felt great, didn't smoke.. and was a Deere


Marin 05-20-2015 01:03 AM

Engine hours are all over the map and there are so many variables in boating, particularly recreational boating, that affect engine health that it is pretty much impossible to come up with any sort of rule.

FWIW, here are some specific data points that don't really mean anything...

1. A good friend in Hawaii runs a small fleet of tuna longline boats. They go out for a month or two, come in, unload, and go out again. My friend likes Volvo engines and his boats, all in the 70' range, are powered with single Volvo Penta turbocharged, aftercooled engines. They are never run over 1500 rpm and they are never shut down unless there is a problem. My friend gets really pissed off if he gets less than 30,000 hours out of an engine before it needs an overhaul. From what he's told me he's rarely needed to get pissed off.

2. Our boat, built in 1973, has just over 3,000 hours on it's two FL120s. They run great so far.

3. I've been told by Bob Smith at American Diesel that back when the Washington State ferries used FL20s for some task or another--- generators, hydraulic pumps, I don't know--- they routinely went 25,000 hours before needing an overhaul.

4, The FL120, assuming proper operation, service, and maintenance, is said to be a 12,000 to 14,000 hour engine in recreational boat service. Where that number came from I have no idea but I've beard it from people who know the engine well, including Bob and our diesel shop.

5. I know of a few FL120s that have accumulated some 8,000 hours and are still (last I heard) going just fine. This does NOT mean they didn't need pump changes, injection pumps overhauled, heat exchangers replaced, etc. along the way. It means the core engines are running fine.

6. I know of some FL120s that never made it to 3,000 hours before packing up in a major way. Due, I'm sure, to operator error.

Delta_JimS 05-20-2015 01:20 AM

Thanks Marin,

That 12-14k data point on the FL120 was the primary one I was looking for.

My Volvo is a great engine (except parts prices), but the high revs and Turbo drive me nuts.
Seriously thinking I would prefer a FL or Perk for my next boat.

eyschulman 05-20-2015 01:48 AM

As many of the above posts hint engine hours as a single criteria is not really significant. How the hours were compiled over how much time and what maintenance was done is often more important. There is also the marine age factor where living in a salt water environment over time will do in the motor and its components. The commercial boats that get high hours do so over a short time and usually with good maintenance. A 1980s engine with low hours and a lot of marine age with poor maintenance may not see 4,000 hours while the same engine on a work boat may go 10,000 hours before its first rebuild and that may happen in only a few years. I personally am very wary of old boats with low hour engines.

AusCan 05-20-2015 03:18 AM

Yes, so many variables.
I used to work for a power generation company who ran a fleet over 1000 1MW modular gensets powered by turbocharged Caterpillar 3516's. These engines ran at maximum load, (above the Caterpillar rated load)

We monitored the wear closely, avoiding over-servicing, but not under-servicing. Oil changes at 700-1100 hrs dependent on oil sample results. Regular adjustment of valve lash and measurement of valve recession.

We averaged about 15,000 hours before needing a top end overhaul 30-50,000 hours before a full rebuild.

One point of interest was the engines that were ran only during peak tariff periods and shut down & restarted daily required overhauls much earlier than the engines which ran non-stop.

The stresses of and engine heating & cooling definitely affect engine life. That is one reason fishermen get much longer engine life in comparison to recreational boats.

Long term shut down periods of marine engines also have a negative effect marine engines. Oil becomes slightly acidic which plays havoc on engine bearings.
Internal corrosion occurs due to due to small undetected leaks in heat exchangers.

High Wire 05-20-2015 05:56 AM

One of the trawlers we chartered with a FL 120 had 11000 hrs on the meter. Don't know its history but it looked pretty much original.
Its rare to hear someone report their engine has worn out in the trawler world. Its usually death by auxiliaries or owners choice.

FF 05-20-2015 06:26 AM

The longest lasting engines seem to be the ones that start , run their time (like a prime generator) , and are only shut down for minor service.

The marine hardest service is no use for months on end , with no protection,endless ideling to charge a batt set , or operation at Flank speed to go kill fish for a few hours.

For most pleasure boaters the engines are KILLED , not worked till worn out.

Bygge 05-20-2015 09:48 AM

Our -73 perkins 6.354 turbo, 145 HP has just over 3000 and starts the second you turn the key and sounds real good though a little "smokey". New rings and bearings by a po about -90 but from what ive heard there were no problem, just enough time to checkup the engine. Here in Sweden the season is short so the boats often stays on the hard about 7 months/year.
Sail on/Tomas

Ski in NC 05-20-2015 10:27 AM

A guy gave me a box of parts from an old wooden boat being cut up. In it was a mechanical Stewart-Warner tach that had a rev counter built in. I think the rev counter clocks the same as an hour meter at 1800rpm, digits are identified as hours.

It showed 56000hrs!! I still have it somewhere. Not sure what engine it was. The boat did some traveling before it died at an old age.

RCook 05-20-2015 11:10 AM


Originally Posted by Delta_JimS (Post 334378)
My Volvo is a great engine (except parts prices), but the high revs and Turbo drive me nuts.

FWIW, my 260 hp Volvo KAD44P, 24-valve, electronically controlled, supercharged and turbocharged, 3900 RPM at WOT, is 17 years old, and I've put 6,080 hours on it so far.

I maintain it religiously, and keep it clean and tidy. Only significant engine repairs were replacing turbo and exhaust elbow at 4,053 hours, and replacing seawater pump at 5,207.

Still runs like a top, uses very little oil, happily cruises at 6 knots and 1350 RPM, or lets me go 16-18 knots at 3000-3300 RPM when I feel the rare need for speed.

Photo from 2013:

Larry M 05-20-2015 11:27 AM

1 Attachment(s)
Our FL SP135 has 8,081 hours. I don't see any reason she shouldn't go 12,000 plus. The oil analysis all looks good. I'd like to think she's just at the end of her break in period. :)

Wayfarer 05-20-2015 02:18 PM

For a second I thought you were going to say 80,000 hours, Larry.

BandB 05-20-2015 04:05 PM

To the simple question of how common, in pleasure boating it's somewhat uncommon simply because most people don't use that much. We do put on over 3000 hours a year but it's not confined to one boat. Far more common is 100-500 hours per year.

In commercial boats it's not really unusual at all.

Now, I'm going to say regular maintenance is a key, but then I'll also tell you I've seen some poorly cared for and abused engines on commercial boats that seem to last forever. Then I think of tractors. Some farmers have incredibly fancy modern tractors, but then there's the farmer with a 40 year old tractor who never even changes the oil, adds some occasionally, and leaves it out in the elements.

However, I do agree mostly with an above comment on peripherals. The engine is the most sturdy piece of equipment but all the other parts added to it will go sooner and if that isn't recognized, the engine will pay the price.

As to comments about engine designs just look at the range of horsepower offered on any engine. We know that being toward the upper middle of that range as we are, the engine is getting worse treatment by our use than if we had one at the lower end designed for heavy load and continuous use. On the other hand we left Fort Lauderdale this morning and are almost to Nassau. So that's the trade-off we made.

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