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Old 08-11-2019, 10:44 AM   #1
City: Vero Beach, Fl
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Engine Hours

I am looking at a trawler that has the Cummins 4bt 3.9 150HP engine. The vessel was purchased new in the mid 1980's by a naval engineer. It has been serviced and maintained very well. The engine has 7000 hours on it. Should I be concerned? What would be the lifespan of this engine if properly serviced and never abused?

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Old 08-11-2019, 11:14 AM   #2
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Given the hours the engine must be well matched to the boat and been well taken care of. As long as you keep the sea water side serviced (no overheating), there is no reason you cannot go to 10-12,000 hours and beyond with regular maintenance.

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Old 08-11-2019, 11:22 AM   #3
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The only way to get even an approximate potential lifespan for that engine is to have an experienced Cummins surveyor do a thorough inspection. Are there running and maintenance logs available? Actual lifespan will be largely dependent on how you run it and care for it.

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
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Old 08-11-2019, 11:37 AM   #4
City: Vero Beach, Fl
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Thanks for the responses. The engine and trawler were maintained very well. No expense spared and all issues were addressed immediately. The original owner is now 93y.o. and this was his baby. He was a marine engineer by trade and designed weapons systems for the navy. There are complete log books of everything done to both the hull and engine/generator since new. The high hours result from multiple cruises around the great loop and the Florida coasts as well as Caribbean. Much of that travel was done between 1500-1800 rpms. The trawlers home port was on the upper Mississippi so much of its life has been spent in fresh water and I would estimate that 70% of the hours have been in fresh water. 7,000 hours gives me some pause but knowing it's history and care; I am thinking it may have a lot of life yet. Just being cautious.
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Old 08-11-2019, 11:47 AM   #5
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Here is a good article comparing gas with diesel marine engines. Its good because it will give you a realistic appraisal of the maintenance of the diesel engine. Based on this article, high hours on a diesel is far better than low hours due to corrosion.

Of course most know that keeping up with necessary maintenance on an engine is better than not doing it, but you will see key items to check to see if this maintenance was done. Based on this article, I'd guess a rebuild will be in your future. Based on what you said about the guy and the boat, I'd still get the boat knowing a rebuild will be around the corner sooner than latter.
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Old 08-11-2019, 12:03 PM   #6
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Engine should have lots of life left in it at 7k hrs. Worst case a 4BT long block is not very expensive.

If it checks out well, worry not.

I'd rather have one with 7k in good shape than one with 1k that sat long term.
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Old 08-11-2019, 12:32 PM   #7
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Those are tough little motors. There are tons of them around in delivery trucks such as Frito-Lay, UPS, Fedex, etc.
Lots of mechanics can work on them.
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Old 08-11-2019, 01:04 PM   #8
City: Vero Beach, Fl
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Given the regular maintenance and use; I am leaning toward its going to be good for quite a while. As ski in nc said it's better that it was used and didn't sit. The owner regularly used the boat up until this spring. He is now too old and has decided to part with it. Thanks to all for the advice.

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