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Old 07-18-2020, 09:40 AM   #21
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Forget hours.
Just get a very good survey w compression check by a locally well known surveyor w a good rep. Engine condition is the bottom line and what really matters. And lots of bad stuff happens to low time engines.


North Western Washington State USA
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Old 07-18-2020, 10:02 AM   #22
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Back to the OP’s question. I don’t think there is enough data in the world to answer the question of how many hours are too many. Years appears to be a better indicator than hours but even that is full of exceptions. When I look at the boneyard, I don’t see boats with crazy high hours. I see abused engines or obsolete engines(cheaper to replace than to repair).

Would I walk away from a 10,000 hour engine? No, but I’m going to assume a rebuild is in the near future but then I might get lucky.

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Old 07-18-2020, 10:41 AM   #23
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AS A simple rule of thumb 3 cubic inches per hp will keep one out of troubble.

Sure HD industrial engines can be worked harder , but boats seem to get farm tractor engine , bulldozer engines , light truck and taxi cab engines .

On the DD 6-71 the rule was between 20hp (forever) and 30hp (almost forever) per cylinder works with Natural engines.
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Old 07-27-2020, 01:48 PM   #24
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I would be very wary of a older boat with low hours. Engines that have not been routinely (monthly) run and brought up to temp will have more problems than a higher hour motor that has been run and maintained.
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Old 07-27-2020, 02:03 PM   #25
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The power vs displacement limit before durability drops off varies significantly between engine designs. For example, the current iteration of the Cummins B series seems to last quite well into the 400+ hp range if operated reasonably and not abused. But the slightly larger displacement Detroit 6-71 will have lost most of its lifespan if pushed to that same power level.

Generally, staying away from the highest ratings of a given engine model will significantly help lifespan. And as you narrow your choices down, do some research on the specific engine models in question (at the power ratings in question) to get an idea of typical durability, any specific concerns to look for, etc.

Compression tests, oil analysis, etc. can all help determine if an engine is healthy, showing significant wear, or has a potential major issue. As others have pointed out, maintenance and how the engines were operated make a huge difference. Think about the gas engines you're familiar with. There are big block Chevies out there in boats with 2000+ hours still healthy and running nicely. And plenty of other people blow them up well before 1000 hours.
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Old 07-27-2020, 02:31 PM   #26
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Lengthy discussion on a 12kw Northern Lights Generator. Has 6700 hours on it - owner feels the slight mainseal engine weep should not have shown up until 10,000 hours, with some reportedly going 15k-30k hours between major rebuilds.

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Old 07-27-2020, 02:56 PM   #27
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Originally Posted by Ski in NC View Post
Oil samples are a useful, yet imperfect tool. I have reviewed hundreds of marine diesel oil analyses. Their value really varies with the type of engines. I have seen Detroit two strokes that had absolutely worn out liners and rings, yet perfect oil samples. I have seen Cummins with flagged (by the lab) high wear metal numbers, yet checked out perfectly and went on for several years of good service.

I tend to focus on Na and K (salt or coolant getting in oil), soot content (oil not changed enough), viscosity, fuel dilution, flags for glycol or water. The wear metals (Fe, Al, Cu, Pb, Tn, etc) get some attention, but these can be really skewed by lots of sitting time.
Ski, you know a lot more about this subject than I do, but my feelings exactly. I had them done on our previous boat, and now this one. Their primary use is to establish a baseline, and then looking for trends over years of usage. I have mine pulled every 2 years. I just reviewed my sample results this am and one came back as yellow "abnormal" for the Trans fluid due to lead. But, the lead amounts in the sample the prior 18 months were higher, but rated as green "good". I called the testing company and turns out the sample was miscoded as far as the Trans type and everything is fine - green.
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Old 07-27-2020, 07:40 PM   #28
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I have two 2002 Cat 3406e rated at 800hp each with 5400 hours.

These Cats have been very well maintained and upgraded per Cat recommendations. Their care is not cheap but they run extremely well and have an expected life cycle of 15,000 to 20,000 hours.

I had a Cat engine specialist do extensive computer diagnostics on these engines, including interpreted oil sampling results and detailed physical inspection of parts and components. This was part of an all day sea trial survey. Not cheap, but bad engines would have been a deal breaker.
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Old 07-27-2020, 08:39 PM   #29
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Originally Posted by boatpoker View Post
Photo below - 1971 Perkins HT6-354 - 20,000hrs when I rebuilt it. It didn't really need a rebuild, I just had nothing to do one winter.

A 3208 natural at 220hp with 3500hrs is barely broken in. A 3208 turbo boosted to 425hp may well be in it's last stretch at 3,500hrs.
I owned a 3208NA in my freezer salmon troller that I had rebuilt at 20,000 plus hours. She needed the rebuild as the crank shaft bearings were just starting to show through the brass.

At the time I had the unit rebuilt the company owner who's people did the re-build told me to track the fuel consumed not the hours ran to define re-build time. He said that at 30,000 US gallons a well cared for 3208 is usually needing the re-build. These were Caterpillar certified mechanics specializing in Cats.

So, as noted, as horsepower increases along with speed and fuel consumption, engine life is reduced sooner.

I suspect most diesel engines may not be the same but are similar?
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Old 07-27-2020, 09:23 PM   #30
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Engine Hours and Condition.

Oil analysis is a good idea, but how do you know how many hours the oil has on it? It seems like it would be best done if the oil is not absolutely new and clean! Regardless of hours, does the engine start after a few revolutions? Like touch the button and she fires up? Another hint: watch the engine when you shut it down. Upon shutdown, just when she kicks over her last couple revs, the engine should stop quickly and jiggle a bit in her mounts, like shudder a bit. In a diesel that indicates good compression. If the engine continues to try to run with the shut-off button pressed, dies slowly, it is a bad sign -- low compression, running on fumes sucked up form the crankcase. General condition of the boat tells you a lot. Even if it has had multiple owners, a clean engine room without leaking accessories, a lot of oil smell, and soot and grime hanging from the overhead beams is good sign. Happy Hunting!
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Old 07-28-2020, 08:30 AM   #31
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There are many factors in hours of any motor. Its a balance of maintenance and how hard she has been worked.
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Old 08-03-2020, 10:26 AM   #32
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I recall talking to yacht captains from Ft Lauderdale who kept their boats on the "New River". It was very apparent that getting a fresh water flush as they entered the new river on their way to home berth made a huge difference in how their engines lasted and even their appearance in general. That would make any fresh water slipped boat more desirable that's equal in salt waters. It's fairly affordable to add a flush kit to your engine and a small hassle to attach the dock hose for 10 minutes every time you take the boat out. Too bad we can never know how hard an engine has been run. But there are clues when you put all the puzzle pieces together.
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Old 08-03-2020, 12:14 PM   #33
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Engine Hours

Originally Posted by Frank60 View Post
I'm searching for a 40 to 50 ft trawler. All of my experience is with gasoline engines. Looking at a few mid-2000's boats. At what point should I start getting concerned about the number of hours on the engines? I'm seeing some in the 1,000 to 1,500 range and others in the 3,500 to 4,500 range. Unfortunately the boats that I like are on that higher end. When would you walk away just based on engine hours?

For example, one is a Grand Banks, Caterpillar engines, 3,200 hours. Another is a DeFever CMY with over 4,000 hours. It seems that the prices are somewhat taking into account the number of hours in comparison to other listings but not dramatic discounts.

I guess that at some point the engines need to be re-built? What does that entail for a diesel?

Appreciate any thoughts on this.

As many have already said how well the engine and for that matter the rest of the boat was maintained and looks has more to do with price than engine hours alone. A visual inspection says a lot of about the seller. If the boat looks neglected, it doesn't matter how many hours it has, within reason. Look at the engine zincs. If they look brand new, beware. But if the log book (if there is one) shows they were replaced every few months, and again just recently that's a good sign. I just bought an older boat from the original owner. Engine hours were low. The seller had his broker do a full survey as well as an engine survey. I personally talked to the the engine surveyor. He had the engine oil and antifreeze analysis done. Both Passed. There was a list of 10-15 things that needed attention. Nothing that alarmed me. He said that even though the boat was older the engine looked like it wasn't abused. I did most of the items on the list myself and hired a Caterpillar mechanic to adjust the valves and remove and clean the inter-cooler and heat exchanger (All of which were on the surveyors list) and all looked very good.

So I feel pretty good that what I got was a well maintained boat.

I would require a survey of the engine as well as the rest of the boat. Have an oil and coolant analysis done. Don't forget the generator if equipped. Make sure the engine zincs are inspected. Review the log book if the seller has one. Discriminating owners maintain their boats better than average. The other piece of advise is look at a few boats, even if you have to travel. You'll get a better perspective of how they were maintained than just looking at pictures and reading descriptions. Avoid the convenience of just looking at listings. Good luck and please post back how the search is going and what you do finally get.

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