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Old 27-01-2016, 13:11   #1
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Engine Hours

Do diesels really wear out? Since charter catamarans are usually significantly less expensive than private boats, they are enticing to see but they usually have high engine hours.

If a charter boat has 3,000 engine hours, but has been well maintained, is this a concern? If you replace the alternator belt, impeller, water pump, and oil filter are you in good shape?
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Old 27-01-2016, 13:25   #2
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Re: Engine Hours

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Originally Posted by lindabarzini View Post
Do diesels really wear out?

If a charter boat has 3,000 engine hours, but has been well maintained, is this a concern? If you replace the alternator belt, impeller, water pump, and oil filter are you in good shape?
There can be somewhat more to it than that, but in general high engine hours doesn't need to be a show stopper.

Other service points would include periodic valve adjustments, fuel filter replacements, periodic flushing of the freshwater system and antifreeze replacement, heat exchanger service, periodic oil sample analysis, maybe new exhaust manifolds... and sometimes replacing some of the bolt-on stuff (fuel pump, alternators, starters, air cleaners, etc.) and all the hoses. On some larger engines, transmission oil coolers, fuel coolers, aftercoolers, etc. but those latter are maybe unlikely in low-horsepower auxiliaries in catamarans.

Still, 3000 hours on a well-maintained diesel isn't necessarily bad. Ideally on a specific brand/model where parts and service is commonly/easily available.

In fact, sometimes 300 hours on a 25 year old diesel could be more of a warning sign.

OTOH, 3000 hours on a not-well-maintained engine... not so good.

You should be able to expect to review service records, and have a mechanical (engine) survey done by a specialist in the candidate engine brand (i.e., don't rely on only a "marine" survey).

-Chris
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Old 27-01-2016, 13:48   #3
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Re: Engine Hours

Diesel engines do wear out but they typically last a lot longer than gasoline engines. 3K is not high for a diesel.
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Old 27-01-2016, 14:02   #4
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Re: Engine Hours

Oh yeah Diesels wear out, and they are often Murdered too, just like batteries.
Fact is, even gas motors will last way more than they ever have in the past, I have 175,000 miles on a Toyota now and there is no real blow-by and no oil consumption.
At 30 MPH average (car keeps up with average speed) that is 5,833 hours. Unless something catastrophic happens it will easily go 250,000. Fact is, I have never, ever worn out a motor, always had the vehicle it was in fall apart, as in just get old. But I maintain one to a high standard. Most motors are fixed when they break, most owner / operators do not understand preventative maintenance.
Just like batteries, the most important thing in determining life of an engine is how it's been treated.
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Old 27-01-2016, 14:20   #5
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Re: Engine Hours

Have the engine compression or better leak down tested. If you don't plan adding many hours, a good engine might never have to be overhauled in your time.
It depends on the manufacturer of the engine and the people operating the engine. On a heavy duty diesel, 3000 hours is just a good break in period. But most recreation engines are light duty. The trend in recreational boats power has been to get to a smaller, but higher hp engine. To do that usually means a turbo is added to an existing design. That brings much more heat to the pistons, rings and sleeves and more pressure on the bearings, head and valves.
For example, my mains, Detroit 671s naturals are non-turbo, about 200hp. Sport fishing versions have turbos and about 485hp. Same design block, rods, crank, head and so on. The non turbo Detroits easily go 10,000 hours in commercial service. The turbo engines 3000-5000 hours between overhauls. In tracing the history of my mains, they went about 20,000 hours before I bought the boat. If the the turbo engine owners would slow below 80% of hp, they could double the hours between overhaul.
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Old 27-01-2016, 14:33   #6
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Re: Engine Hours

Quote:
Originally Posted by lindabarzini View Post
Do diesels really wear out? Since charter catamarans are usually significantly less expensive than private boats, they are enticing to see but they usually have high engine hours.

If a charter boat has 3,000 engine hours, but has been well maintained, is this a concern? If you replace the alternator belt, impeller, water pump, and oil filter are you in good shape?
First - Yes, all mechanical devices are constantly wearing.

Everything else being equal, engine hours is a measure of life expectancy.

Unfortunately, everything is not equal.

It is reasonable to assume that:

1. A marine diesel engine can run 10,000 hours or more, prior to requiring a major overhaul or replacement.

2. Age has a detrimental affect on the engine, especially peripheral equipment.

3. A well maintained engine will live longer than a poorly maintained engine.

4. A non-abused engine will live longer than an abused engine.

5. Some engine makes/models will last longer than others due to superior design and manufacturing.

6. Some engines of the same make and model will last longer than others, due to metal quality, dimensional tolerances, and conditions at time of manufacture.

As you can see, there are a lot of variables that can affect engine life expectancy, other than just hours.

Take the following scenarios:

1. An engine that has 100 good hours put on it per year will have 2000 hours after 20 years.

2. An engine that has 20 good hours / year on it will also have 2000 hours after 100 years.

3. An engine that has 200 bad hours per year on it, will have 2000 hours after 20 years.

4. An engine that has 20 bad hours on it per year, will have 400 hours after 20 years.

In this scenario, even though engine 4 has far fewer hours, I would pick engine 1, every time!

So what are good hours?

1. Hours run with fresh oil and filter.
2. Hours run where no defects are present.
3. Hours run to 75% full load.
4. Hours run at proper operating temperature.
5. Proper break-in.
6. Proper warm up and cool down.

Due to the nature of charter boats:

1. Operators only care if it works during their use.
2. Operators may not know how to extend life.
3. Maintainers may need to get it back in service before 100%.
4. Increased likelihood of abuse.

I would not expect a charter boat engine to last as long as the engine of an one of a knowledgeable owner with pride of extending proper maintenance.

However, the professional service people of the charter company may actually due a better job, than a well intentioned private owner.

Does this help?

Note that engine oil analysis, really only tells the story of the engine oil sample withdrawn.

Oil from an engine due for change, will tell a lot more than oil from an engine just changed.

Oil analysis is not the end all, be all, tell all solution for engine life expectancy.

Clean engine oil today only means it has been recently changed, not that it has been changed at proper intervals (or even at all) over the entire engine life.

Sorry if this sounds self-serving but, well documented records performed by a competent, marine service provider are a pretty good indicator of how well an engine has been treated.

Ask if any water pump service was ever the result of a failure.

An impeller replaced every 4 years pre-emptively is vastly superior vs one replaced every 2 years as a result of failure and overheating.

Ramblin Rod
Marine Service Provider
About Sheen Marine
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