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Old 06-10-2018, 11:32 AM   #1
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Engine Hours When Shopping

I come from the sailing and aviation world. I'm in the beginning stages of shopping for a Loop Boat. While I am very familiar with aircraft engines, marine engines are another matter. Please help me to learn what is a reasonable expectation.

I'm only interested in diesel engines. What range of hours is considered a reasonable use? How many hours should you expect from a marine diesel engine before an overhaul is required if it is properly serviced and well treated? What are reasonable annual hours of use? Are there brands of engines that are considered to be superior? Are there brands that should be avoided at all costs? Please tell me why.

Obviously, I don't know enough to ask all of the questions I need to ask, so I would appreciate the education and any experience that you might want to share.
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Old 06-10-2018, 11:37 AM   #2
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Hi Orvil

Welcome

Go to search feature. Month o' reading there on best/worst engines!
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Old 06-10-2018, 12:02 PM   #3
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You'll find lots of information and even more opinions on this topic here. Search, read, consider but make up your own mind. Also consider joining boatdiesel.com for even more detailed info on specific brands and model engines ($20/yr)

I think the best advice I got was to narrow down your search to the boat you're after (size, draft, air-draft, # heads, # staterooms, layout, etc) and it comes with what it comes with for engines. You can then disqualify or qualify a specific boat based on your engine/hours/manufacturer/maintenance preferences. Most boats came with more than one engine manufacturer based on the original owners preference so if you find the perfect boat sometimes it's available (in due time) with your preferred engines.

Most trawlers are run lightly, with few hours per year over a lifespan (<5000 hrs on a 10K - 20K hr lifespan in a 20+ year old boat). One big difference for recreational marine engines over aviation is we're not required to perform maintenance at certain intervals. This is both good and bad. It also means ensuring that previous owners performed proper maintenance and care is critical. Additionally, a lot depends on what you want, how DIY you aim to be (self service or call a mechanic?).

When you find "the boat" get a separate engine survey (in addition to the general survey) from a qualified mechanic for those engines. That, more than the badge on the rocker covers will tell you when to buy and when to run.

For me, I didn't have a specific preference that would cause me to walk away. We ended up finding the boat first and it happened to come with twin Ford Lehmans with 1,100 hours on them (on a 37 y.o. boat). Given the low hours on old engines we had an engine survey performed during the sea trial. Other than some noted missing upgrades (a more modern raw water pump, engine coolant overflow tank, etc) the mechanic's report noted nothing of significance. His comment was "I'd take these engines to Alaska tomorrow". Given I'm a DIY guy (and get about 50% of my joy of boating by working on my boat) the mechanical Lehamns were the perfect set of engines for me own.

For you it might be different.

Of course then there is the question of twin engines vs single, which generate a religious debate on these forums about every month (that and anchors).

Good luck, research everything and happy hunting!
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Old 06-10-2018, 12:07 PM   #4
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Well, I did a search and a link to a link gave me this article. For those of us who were taught engine hours and automotive miles this article makes a great point about "marine age".

https://www.sbmar.com/articles/marin...diesel-engine/
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Old 06-10-2018, 12:27 PM   #5
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Aircraft engines have manufacturer recommended (or is it required) "time between overhaul" or TBO. That works because aircraft engines are operated within a very narrow power band.

Marine engines don't work that way. Relatively low speed normally aspirated marine engines can last for 10,20,30,000 hours if operated and maintained right. High output, turbocharged engines such as used in sport fishermen might not last 3,000 hours.

As noted above, I wouldn't worry about buying any trawler engine with less than 5,000 hours. But I would look for signs of aggressive operation or poor maintenance which can lead to premature wear. A quick start from cold and little or no crankcase blowby are good indicators.

I would buy a marine engine with 10,000+ hours but I would look more closely at the above issues.

There is no absolute answer to your question.

David
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Old 06-10-2018, 02:59 PM   #6
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As Airstream345 said: joining http://boatdiesel.com/ is a cheap/good idea. You can find info on most engines and their PDF library has manuals on many engines. People posting in their forums are often oem techs or long experienced mechanics.

In general medium duty engines last longer than recreational duty engines and heavy duty last longest of all. Non-turbo engines outlast turbo engines.

But how they were run, cared for, and maintained has the biggest effect on their lifespan. Records/receipts of regular and timely oil changes are probably the best indicator. Only an engine survey by an experienced mechanic can find defects. And then not every one.
There is no magic number for yearly hours. 500 cared for hours is better than 10. Many engines will go 10,000 hours with good care. Some much longer. But engines run wide open with too few oil changes can need a rebuild in 1500 hours. I've rebuilt many diesels.
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Old 06-10-2018, 09:10 PM   #7
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Pleasure engines almost never wear out, but that does not mean they don’t fail, or simply get to a point where it is no longer economical to continue fixing or maintaining when something major breaks.

Engine hours can tell you when to change the oil, but little else. They get used because humans want to measure something in the absence of a better measure. A maintenance log would be best, but few have them and even fewer are complete and trustworthy.

To make things even less intuitive, I’d suggest that a high hour boat, all things being equal, more often than not will be a better choice than the low hour boat. A boat that sits ages, a boat that gets used tends to get maintained.
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Old 06-10-2018, 09:22 PM   #8
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I know of 2 boats for sale same age one has 370 hours and the other has 2500 knowing the boats and the owners Id take the 2500 hour boat over the 370
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Old 06-10-2018, 10:11 PM   #9
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Originally Posted by Orvil View Post
Well, I did a search and a link to a link gave me this article. For those of us who were taught engine hours and automotive miles this article makes a great point about "marine age".

https://www.sbmar.com/articles/marin...diesel-engine/

Orvil some good info already on this thread for you but you've already found the most important in that article right there. I'm sure others will give you specifics on different brands if you have particular boat/engine combinations. I can recommend Cummins. Have always found them a good engine. I've had Cat's which were not bad and Volvo's that were expensive on parts.


Brett
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Old 06-11-2018, 12:21 AM   #10
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Orvil some good info already on this thread for you but you've already found the most important in that article right there. I'm sure others will give you specifics on different brands if you have particular boat/engine combinations. I can recommend Cummins. Have always found them a good engine. I've had Cat's which were not bad and Volvo's that were expensive on parts.


Brett
I have experience with Cats, Cummins, Volvo, Yanmar. I wouldn't shy away from any of those, with certain caveats: Cummins are great modern engines. The old 555 "triple nickel" has a bad rep, though I don't know anyone who has actually had a problem with one. Cats are great modern engines too, though the old 3208 would block out the sun on a cold startup. I had a newer 6 cyl Cat in a motorhome that was a very reliable engine. The same as several friends had in their boats with no issues. My own boat came with Volvos, that I changed up to other Volvos. I have not experienced the complained of "expensive to maintain", as the parts needed to maintain those engines are no more expensive than those to maintain my Motorhomes with Cat or Cummins. Talking only of things like oil filters, belts, hoses. None of those engines need much else on a regular basis.
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Old 06-12-2018, 06:01 AM   #11
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Originally Posted by Orvil View Post
Well, I did a search and a link to a link gave me this article. For those of us who were taught engine hours and automotive miles this article makes a great point about "marine age".

https://www.sbmar.com/articles/marin...diesel-engine/
Interesting article, but heavily based on the aftercooler (though used as an example of good versus bad maintenance). I also am not quite convinced on his concept of "marine life," since he seems to be suggesting that the environment is harsher than for aircraft or auto engines. This is obviously true but we can't forget that marine engines are marinized to meet that environment. He discussed the way the engine was built was a big part of the problem - well that wasn't driven by the marine environment.

BTW many engine do not utilize aftercoolers.

As to hours. The comments above are great. It is not the hours but how the engine was maintained and also run. When we were looking at boats three years ago we were looking at early to mid 2000 boats and most were around 1-2K hours. When we met Sonas she had ~4800 hours on her engines. We had the engine survey done by Shearwater out of Stuart (they are the people used by PassageMaker for their diesel seminars) and they cleared the engines - as did my mechanic here in Jax when he worked on them and he services the St John's pilot boats.

So engine hours are just one variable in your decision, and I would even argue not one of the important ones.
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Old 06-12-2018, 06:03 AM   #12
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Originally Posted by Orvil View Post
Well, I did a search and a link to a link gave me this article. For those of us who were taught engine hours and automotive miles this article makes a great point about "marine age".

https://www.sbmar.com/articles/marin...diesel-engine/
Interesting article, but heavily based on the aftercooler (though used as an example of good versus bad maintenance). I also am not quite convinced on his concept of "marine age," since he seems to be suggesting that the environment is harsher than for aircraft or auto engines. This is obviously true but we can't forget that marine engines are marinized to meet that environment. He discussed the way the engine was built was a big part of the problem - that wasn't driven by the marine environment.

BTW many engines do not utilize aftercoolers.

As to hours. The comments above are great. It is not the hours but how the engine was maintained and also run. When we were looking at boats three years ago we were looking at early to mid 2000 boats and most were around 1-2K hours. When we met Sonas she had ~4800 hours on her engines. We had the engine survey done by Shearwater out of Stuart (they are the people used by PassageMaker for their diesel seminars) and they cleared the engines - as did my mechanic here in Jax when he worked on them and he services the St John's pilot boats.

So engine hours are just one variable in your decision, and I would even argue not one of the important ones.
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Old 06-12-2018, 06:13 AM   #13
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I haven't seen mention of Detroits. I note many of them require rebuilds at around 2,000 hours---very expensive. My wife and I love Hatteras motoryachts but I'm afraid of them since the vast majority have Detroits. Do I worry too much?
Thanks, Howard
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Old 06-12-2018, 06:22 AM   #14
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Originally Posted by Airstream345 View Post
You'll find lots of information and even more opinions on this topic here. Search, read, consider but make up your own mind. Also consider joining boatdiesel.com for even more detailed info on specific brands and model engines ($20/yr)

I think the best advice I got was to narrow down your search to the boat you're after (size, draft, air-draft, # heads, # staterooms, layout, etc) and it comes with what it comes with for engines. You can then disqualify or qualify a specific boat based on your engine/hours/manufacturer/maintenance preferences. Most boats came with more than one engine manufacturer based on the original owners preference so if you find the perfect boat sometimes it's available (in due time) with your preferred engines.

Most trawlers are run lightly, with few hours per year over a lifespan (<5000 hrs on a 10K - 20K hr lifespan in a 20+ year old boat). One big difference for recreational marine engines over aviation is we're not required to perform maintenance at certain intervals. This is both good and bad. It also means ensuring that previous owners performed proper maintenance and care is critical. Additionally, a lot depends on what you want, how DIY you aim to be (self service or call a mechanic?).

When you find "the boat" get a separate engine survey (in addition to the general survey) from a qualified mechanic for those engines. That, more than the badge on the rocker covers will tell you when to buy and when to run.

For me, I didn't have a specific preference that would cause me to walk away. We ended up finding the boat first and it happened to come with twin Ford Lehmans with 1,100 hours on them (on a 37 y.o. boat). Given the low hours on old engines we had an engine survey performed during the sea trial. Other than some noted missing upgrades (a more modern raw water pump, engine coolant overflow tank, etc) the mechanic's report noted nothing of significance. His comment was "I'd take these engines to Alaska tomorrow". Given I'm a DIY guy (and get about 50% of my joy of boating by working on my boat) the mechanical Lehamns were the perfect set of engines for me own.

For you it might be different.

Of course then there is the question of twin engines vs single, which generate a religious debate on these forums about every month (that and anchors).

Good luck, research everything and happy hunting!
This is good advice. Narrow down you boat choice first and then consider the engine(s).
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Old 06-12-2018, 07:42 AM   #15
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Originally Posted by Orvil View Post
Well, I did a search and a link to a link gave me this article. For those of us who were taught engine hours and automotive miles this article makes a great point about "marine age".

https://www.sbmar.com/articles/marin...diesel-engine/
Insightful article, thanks! I'm VERY pleased we keep and use our boat in freshwater - only!
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Old 06-12-2018, 11:11 AM   #16
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I haven't seen mention of Detroits. I note many of them require rebuilds at around 2,000 hours---very expensive. My wife and I love Hatteras motoryachts but I'm afraid of them since the vast majority have Detroits. Do I worry too much?
Thanks, Howard
Many of them require rebuilds at around 1,000 hours even. Many of them have also lasted longer than the boat. You are going to have to be more specific here. A lot more specific. The problem is that Detroits by their very nature are incredibly adaptable to many different applications. They can be run easy and they can be easily(relatively) built for high hp/litre and run hard. Many detroits have been put into battle wagons, where the ability to take a 60 foot sportfish and blast (almost literally) far offshore to fish and 20+knot speeds and then back in an afternoon is both prized and cherished. The engines don't last. Or do they? Because they get rebuilt over and over. Maybe high cost, but some incredible performance. What does that have to do with Trawlers? Not much. A Detroit in a "trawler", lets say semi displacement and a 50ish LOA vessel running at <200 hp. Its going to last a long long long long time.

Bottom line, Detroits are incredible engines, well proven and "can" be set up for your purposes without feeling like you are going to have them apart every season. Parts available in every port and lots of guys that know how to work on them.

Besides if we are dealing in "common knowledge" then you don't have to ever change the oil, just wipe under them after running and add another quart.

I think what may not have been brought up in this thread is the overarching belief that "diesels just run and I never have to maintain, fix or generally spend money on them if I just buy the right label". I don't know what sales brochure that got started in, but its repeated in some slightly veiled manner all the time. It doesn't exist and never has. One mans rebuild is another mans winter maintenance program that you rarely hear discussed. Its easy to not get the full picture.
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Old 06-12-2018, 12:25 PM   #17
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I think what may not have been brought up in this thread is the overarching belief that "diesels just run and I never have to maintain, fix or generally spend money on them if I just buy the right label". I don't know what sales brochure that got started in, but its repeated in some slightly veiled manner all the time. It doesn't exist and never has. One mans rebuild is another mans winter maintenance program that you rarely hear discussed. Its easy to not get the full picture.
Good point. Every spring, regardless of hours put on them, I have a full mechanic service on the engines plus whatever they recommend. This past spring it was flushing out the heat exchangers, replacing a fuel injector valve, an engine mount and RW pump on the NL generator. None of these had failed or prevented the engines from running, but were preventative.

Could some of this have been deferred? Maybe. But I bow to the guys who know what they are doing.

So if there are owners out there who, because of the cost or bother, do defer or maybe even ignore, then the number of hours on the engine won't matter.
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Old 06-13-2018, 06:02 AM   #18
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"I haven't seen mention of Detroits. I note many of them require rebuilds at around 2,000 hours"


This is for the sport fish folks, If a DD 71 series is used at 20-30 hp or less per cylinder the life is great .


EG a 6-71N at 120-180 hp will last a long time.


The lower HP can be had at about 1200 RPM, smooth and quiet
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Old 06-13-2018, 07:21 AM   #19
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"I haven't seen mention of Detroits. I note many of them require rebuilds at around 2,000 hours"


This is for the sport fish folks, If a DD 71 series is used at 20-30 hp or less per cylinder the life is great .


EG a 6-71N at 120-180 hp will last a long time.


The lower HP can be had at about 1200 RPM, smooth and quiet
Per Fred's input as well as several others' input on posts:

Self evident that nearly any engine, diesel or gasoline, last a long, long time when treated correctly in maintenance schedules as well as not overtaxed in RPM or over loading. Be gentle to an engine and it will be kind to you by lasting a long time. Anything can be broken by too much stress, too much heat, too many repeated part interactions, too few maintenance applications.

Simple analogy I'd like to provide. Recall when you were a kid and tried to [or were successful in accomplishing] breaking a metal coat hanger's shaft of metal apart by bending it repeatedly? Also recall that it would not break if not bent sharply and in very fast bending motions that raise the heat of the metal until failure occurred... and the hanger's metal shaft material heated as it deteriorated at point of bend? - - > Think what the metal in an engine is going through if continually run very fast or overloaded that exacerbates the production of heated metal fatigue

On engines: Fast/overloaded/poor-maintenance = costly repairs. Gently use with thoughtful maintenance schedules = decades of enjoyment and fun use!
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