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Old 16-04-2020, 20:15   #1
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How many hours is too many?

I'm looking at a 91 Catalina 30 with an M25 that has about 4000 hours, alternator and injectors done in the last 2 years. Fresh water.

What should I be looking for with respect to condition, other than the obvious things like leaks? Apparently it was 'looked after' but I'm uncertain how many hours before a rebuild, and what other parts may need attention with that many run time hours. Shaft bearings etc.

Also, what's the typical cost to rebuild, assuming you do it in boat.
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Old 16-04-2020, 21:05   #2
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Re: How many hours is too many?

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Originally Posted by pbyrne View Post
I'm looking at a 91 Catalina 30 with an M25 that has about 4000 hours, alternator and injectors done in the last 2 years. Fresh water.

What should I be looking for with respect to condition, other than the obvious things like leaks? Apparently it was 'looked after' but I'm uncertain how many hours before a rebuild, and what other parts may need attention with that many run time hours. Shaft bearings etc.

Also, what's the typical cost to rebuild, assuming you do it in boat.
There is no way to answer the "how old is old" question. The last two boats I have owned each went over 10,000 hours, and are still going without ever opening up the engine. Other engines are dead before 4000 hours.

For a mistreated diesel engine, 4000 hours might be old. For a well cared for one, it is not even middle-aged.

Look for: Good compression. Good oil pressure. An oil analysis might find a few problems.

To keep it running:
Clean fuel.
Oil changes.
Adjust valve clearances on schedule.
Change timing belt on schedule.
Avoid overheating.
Avoid running cold.
Maintain the exhaust system to keep water out of the engine.
Let it warm up before running hard, and after running hard, let it cool down before shutting down.
When running long runs at cruising speed, open up the throttle to full every couple hours for 15 minutes.

In general, replace things like water pump impellers and belts BEFORE they break and cause other problems.

LOOK at your engine every day you use it. Preferably while it is running.
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Old 17-04-2020, 01:31   #3
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Re: How many hours is too many?

Marine engines and generators have design ilfe of 5,000 hours.
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Old 17-04-2020, 02:10   #4
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Re: How many hours is too many?

Greetings and welcome aboard the CF, pbyrne.

The 5,000 - 8,000 hr figure is often quoted.

Here's another professional viewpoint:
"Engines have a “design life”...
In our fishing applications, both propulsion and auxiliary engines might be expected to operate for 20,000 hours without major overhaul in “typical” usage–if “typical” exists. Overloading or poor maintenance practices will radically reduce this service life. A good combination of loading and maintenance can increase the service life beyond this number. We have many John Deere and Kubota engines in service with in excess of 30,000 hours without major overhaul...
... As you can see, there is no simple answer to this question."

Much morehttps://www.frontierpower.com/resour...l-engine-last/
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Old 17-04-2020, 02:24   #5
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Thumbs up Re: How many hours is too many?

A verry strange statement ,as a diesel machanic with over 50yrs in the marine trade ,a shipwrights boatbuilder ,trade trained qualified diesel fitter ,mechanic ,I am verry interested where this sweeping statement is based ,have seen small twin Volvo penta ,driving an irrigation pump,running like a clock at 24k hrs no electrics hand start ,also a air cooled lister 3 cyl gen set running for 9 yrs with verry little maintaince,and an 8l3 Gardner in an 80 ft trawler at 90k hrs still strong ,. Maybe some small turbo charged highly stressed poorly maintained engines will have a short life ,look after them and they will look after you .,i
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Old 17-04-2020, 03:29   #6
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Re: How many hours is too many?

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Originally Posted by Michael Cobbe View Post
Marine engines and generators have design ilfe of 5,000 hours.
Disagree strongly with this sweeping generalization. Components on the engine have service intervals that may include rebuild or replacement, but a well maintained and serviced naturally aspirated diesel engine will easily go 10,000 before it wears out. On the other hand, hi-output turbo/super charged Diesels common on sport fishing boats may be toast at 3500 hours (though in all fairness, have traveled at 25+ kts vs 7). That said, I had a Universal in a Newport 28 many years ago that didn't strike me as a particularly robust engine, but I was not as knowledgeable in Diesels so it could have been me.

To the OP : as others have said, compression check is a good indicator of wear of piston rings and/or valves. Wear accelerates when there isn't enough oil or the valves are allowed to get out-of-adjustment.

Unfortunately, checking compression on a diesel is much more difficult than a gas engine - you have to remove each injector, and it requires some sort of adapter which varies by injector. Net is that it can be expensive to have compression checked unless your mechanic happens to have the right adapter.

First engine check is cold start. Make sure engine is stone cold. Feel the oil pan and the coolant tank. Engine should start within a couple revolutions - not unusual for an engine to start within a half revolution. If it takes more than about 3-seconds of cranking, there may be a compression issue.

Second check would be exhaust. There may be some mild oil in the exhaust with a minor slick. Small amount of blue/grey smoke is not uncommon, but should disappear within a few minutes. Once warmed up, engine should idle smoothly without "loping" (RPMs varying up/down). Sustained or excessive smoking/oil slick or uneven running may be a sign of worn injectors or injector pump. Steam is normal depending on ambient temperature

Third check is blow by. If the cylinders are not holding compression, the pressure is getting past the rings or the valves which then pressurizes the crank case. A visual dockside check is to bring up the RPMs to about 1000 (neutral) and remove the oil fill cap on top of the valve cover. If there's a lot of escaping air - enough to float a tissue or paper towel, especially if it's laced with oil, there may be a compression issue.

Fourth check is underway sea trial. Engine should be capable of running WOT for 10-mins without blowing too much black smoke or overheating. Personally, this is where I want the owner's representative to drive the boat - if it does overheat, not my problem.

Finally, oil analysis. This will generate some strong push-back from other CF members. . It's a holy war - many feel its a waste of time and money especially with a single data point vs sustained trending. Personally, there is enough data in a single oil sample to make it worth the $40 to pull a sample. At the very least, it will tell you if there is sodium - salt water in the engine. There is a chance that the owner has recently replaced the oil, perhaps to hide a known defect. Check the oil filter - many mechanics use a Sharpie to say when the oil was last changed. Also pull samples of transmission fluid (less likely to have been changed) and perhaps coolant. Pulling the sample and interpreting it is not as straightforward as you'd think, but it's a good start.

OP mentioned checking for leaks. Leaks first show up as slight weep or white fuzz. These should all be remedied asap. There is no such thing as an acceptable leak on a boat. Bilge should be dry.

Good luck.
Peter
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Old 17-04-2020, 04:07   #7
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Re: How many hours is too many?

I think Universal engines were mostly based on Kubota engines which I bet were still industrial tough in 90s as today. Not sure about that model. Agree with all posters. Also note that even if there was a mythical 5000 hour ceiling, thatís 10 years of local cruising at 100 hours per season which is a lot. I am presuming local cruising in the C30
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Old 17-04-2020, 04:21   #8
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Re: How many hours is too many?

Of course that said I repowered a 32 year old Yanmar that had only 2600 hours with a Beta 50 because it had apparently been run lightly and ran poorly. And the power curve on the Beta is at a much better RPM range than on the old yanmar.
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Old 17-04-2020, 04:28   #9
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Re: How many hours is too many?

we have a pair of yanmar 4JH2TE with abt 6800hrs. been well maintained and both going well.

even though turbo and comparatively high reving (think top is 3600 rpm although we tend to use no more than 3200), these engines should see 10,000hrs if we keep looking after them.

oil changes (40w) every 150hrs etc etc

cheers,
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Old 17-04-2020, 05:55   #10
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Re: How many hours is too many?

There is nothing wrong with stating that marine engines have a design life limit of between 5 and 8 thousand hours.
It’s probably very correct for the majority of our light weight high speed Diesels, there is a difference between a Yanmar, a Volvo and a Gardiner.
That doesn’t mean that’s how long they will last necessarily, all it means is that the engine was designed to last at least that long under some kind of mission profile that the designers use, if you don’t fit that profile, your motor will most likely last a different number of hours.

Aircraft engines have what is called a TBO, or time between overhauls, for many aircraft it’s a requirement to overhaul the engines at that hour level or less.
I have seen many engines that didn’t make it to overhaul, they failed before then, often losing a cylinder. However when I tore my IO-540 down right at TBO because I had a prop strike, I decided to overhaul it, I had to take it out and tear it down for the prop strike inspection, why not reset the overhaul clock?
Well, every single hard part in the motor met new specs, not serviceable, but new specifications.
So it depends tremendously how an engine is both maintained and operated.
Sportfishermen will often go through good quality motors in very little hours and be well maintained because they will often run the snot out of them, it’s not uncommon at all for them to run 200 off the top, meaning 200 RPM below wide open, and that causes excessive wear and a short life.
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Old 17-04-2020, 08:51   #11
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Re: How many hours is too many?

Check the exhaust mixing elbow.

Most designs will rust through, so the need to replace is apparent.
Some designs, however, build up sooty rust internally, until the passage for wet gases is diminished or even blocked. Engine becomes choked, and many diesel mechanics will diagnose it as impaired fuel delivery (injectors, high-pressure pump, etc.) Only way to tell is to dismount the elbow and look inside. Ask me how I know.
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Old 17-04-2020, 09:03   #12
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Re: How many hours is too many?

Check all the rubber hoses especially the exhaust hoses which can be a bitch to replace. If they are sost and supple, great. If they are hard, replace. Time consuming job.
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Old 17-04-2020, 09:30   #13
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Re: How many hours is too many?

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There is nothing wrong with stating that marine engines have a design life limit of between 5 and 8 thousand hours.
Itís probably very correct for the majority of our light weight high speed .
There is nothing wrong with saying it except it is just a made up number with NO justification at all, and I have no idea what "design life limit" means.

And the fact that you think "it's probably very correct" doesn't change the fact that it was just pulled out of someone's butt who wants to sound like they know something.

By that rational there "would be nothing wrong" with me saying, "a recreational marine diesel is designed to last 1500 hours," or "20,000 hours." It's all nonsense unless you actually KNOW what the designer of the engine specified.

I have NEVER seen a diesel die at 4000 hours that hadn't been significantly abused in some way. Now to be fair, typical recreational sailboat usage of an hour every other week for 10 years is pretty damned abusive...
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Old 17-04-2020, 09:42   #14
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Re: How many hours is too many?

I can explain design life limit, any intelligent designer will during the design specify how long something is expected to last, under a specified mission profile, meaning how hard is it to be operated at what RPM, constant or changing loads etc.
Then all parts are specified or designed to meet or exceed that hour level. It does no good to build an engine that will last 10,000 hours, but the bearings won’t go 3,000.
The design life limit is to a great extent what determines the cost of the engine to manufacture.
In speaking with GE aircraft design Engineers I was told that they could easily build a 30,000 hour turboprop, but it would cost so much it wouldn’t sell.
I’m sure that a 30,000 Diesel is possible too, and again it would cost so much it wouldn’t sell.

Sort of like car tires, different ones depending on mission will have vastly different number of miles they last, its specified on the sidewall, a teenager may wear out a set in half that number of miles, and Grandma may get at least twice the expected life.
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Old 17-04-2020, 09:43   #15
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Re: How many hours is too many?

Quote:
Originally Posted by Michael Cobbe View Post
Marine engines and generators have design ilfe of 5,000 hours.
That will depend very much on the engine. Many "manufacturers" of marine engines buy the blocks from outside sources, some of them industrial blocks rated for 10,000 hours or more.
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