CAT 3126B Service Life

Hi there,

We’re considering a ~50’ trawler with twin Cat 3126B engines that have approximately 4,500 hours on them. The boat looks well maintained both from a structural and a mechanical perspective.

My question is regarding the Cat 3126B hours; are there any benchmarks of when these engines will reach their designed service life? Are there any test that can be done by a Cat certified engine surveyor that can clue me in to what I can expect from the engines?

Are there any large maintenance items that I should ensure have been already performed?

Thanks - Jim

CAT usually base their longevity on #gallons burned not hrs. Of course the M rating of each engine compared to it’s actual use is important. Practically speaking, your best guide will be the boat maintenance records coupled with your general impression of how the boat overall has been maintained. Oil & other fluid analyses may pick up big issues if oil not changed recently, but are most useful if done serially to identify trends.

That is not a lot of hours for maintained engines. Flatswing is correct, have a CAT tech hook his laptop up to them and see whats what. I would expect 20,000 hrs before a full rebuild or repower.

20,000????? Not o sure bout that

Arc said:

20,000????? Not o sure bout that

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Why not? Cat engines go for way more hours than that in heavy equipment,trucking and industrial applications... Why do you doubt 20K hrs? Keep the fuel clean, keep the oil changed and regular oil analysis, service the coolers, other routine maintenance.

JMO but those engines have lots of life left if run AND looked after properly.
The catch is how were they maintained, RECORDS?
Mtce. Log?
History of oil testing?
Propping. If not attended to properly can seriously shorten an engines expected life.
How were they run?

YOu need a good mechanic versed in , hopefully those engines.

3126s aren't necessarily the best reputed of Cat engines, but they're certainly not bad. If they've been cared for well enough to make it to 4500 hours, I'd get them looked over by a good tech. If they still check out healthy, then I'd expect plenty of life remaining.

If run hard, they could be in rough shape. In fact, I doubt they were run hard because then I would not expect them to have made 4500hrs.

SOF- This is a 7 liter block putting out a max of 450hp. Nothing like the continuous rating engines Cat puts in heavy equipment, road vehicles and commercial vessels. The continuous rated versions of this block are in the ballpark of 200hp.

Also, these engines have a reputation (450hp version) of having poorly managed condensation in the charge air cooler which corrodes valves and cylinders after shutdown from a hard run. Very much noticed in sportfish where they are expected to run hard.

To the OP- Get a cat tech to download the run history of the engines. If run at hull speed (like under 1500rpm) they generally will not have the condensation issue.

Get the tech to sea trial it and measure blowby flow per Cat's technique. That will assess cylinder/piston ring condition.

If run easy, even though they are capable of 450hp, they can last very long. If they were truly run at trawler speed, they could be the 20k hr engines mentioned.

In a 50 foot trawler those engines will last a very long time. It would be interesting to look at the travel log. If the P.O. routinely covers 100 or more miles in a fairly short day, he is pushing those engines for all they are worth. If, on the other hand, he generally goes 40 - 50 miles in a 6 - 8 hour travel day you can assume he is just chugging along at 1,800 rpm
doing about 7 or 8 mph then the engines will last forever.

pete

Ski pretty well nailed it with these engines.

If the after coolers are jacket water cooled, you're in luck. If raw water, if they've not had the after coolers pulled and cleaned in the past 5 years be careful.

As mentioned earlier, engine longevity is usually a relationship between maintenance and quantity of fuel consumed. How do you get that data? You can’t, you can inspect the engines and the records for maintenance and then it’s an educated guess on how hard the engine was used.

CAT 3208 came in several HP ratings from 150hp to 435hp. If I found any of these engines in a displacement hull I would guess that you have a 20,000 hour engine. If I found these engines in a sportfisher I would still go with 20,000 on any engine below 350HP. At 375HP and up my guess is less but I don’t have enough experience with sportfishers to tell you how much less.

I did get 28,000 hours out of an Isuzu engine before I sold it. The engine was still working fine but the valve guides were completely worn out. The buyer slapped a new head on the engine and off he went.

Cat 3126 Engines. I had a pair of these in a GB 50' trawler ran perfect.

The best Cat engine surveyor in the world is in Stuart FL. Name is Tim Caruso and he only does Cat marine engines. Visit his website at Marine Diesel Anallaysts, Inc. and read his biography (Cat Engine Surveyor.com) . He now does Lugger too.

Mike Negley said:

The best Cat engine surveyor in the world is in Stuart FL. Name is Tim Caruso and he only does Cat marine engines. Visit his website at Marine Diesel Anallaysts, Inc. and read his biography (Cat Engine Surveyor.com) . He now does Lugger too.

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Agreed Tim is great. He came highly recommended to us. He did a very thorough survey of our JD and NL generator, and afterwards we got a complete and very useful debrief. (We couldn't be there for his work -- covid, you know.)